The Guadalcanal Air Campaign’s “Horseshoe Nail of Victory”

It’s damned rare, when you read the histories of the Second World War, that you can definitively find a place where one man, with the right skills, at the right place, at the right time, provided a make or break/victory or defeat  level of difference in a military campaign with his contributions.  Let alone one so central to the identities of the US Navy and US Marine Corps as the Guadalcanal campaign. Yet, for the period of September 1942 and March 1943, there was one US Marine non-commissioned officer who did just that.

He was Master Technical Sargent Dermott H. MacDonnell.  His performance as chief radar operator for Marine Air Group 23’s (MAG-23) SCR-270 radar made the difference between keeping and losing daylight air superiority over Henderson Field in the darkest days of the Guadalcanal campaign.  He was the Guadalcanal Air Campaign’s “Horseshoe Nail of Victory.”

MTSgt Dermott H. MacDonnell at base of SCR-270 radar on Guadalcanal
MTSgt Dermott H. MacDonnell at base of SCR-270 radar on Guadalcanal.  His performance with this radar won and kept air superiority in the darkest days of the Guadalcanal campaign Source:  Marine Corps Historical Archives, courtesy of MACCS History

How A USMC Radar NCO Became Guadalcanal’s  “Horseshoe Nail of Victory

Most people at one point or another have heard Benjamin Franklin’s “For Want of a Nail…” parable of how a lost horseshoe nail meant the loss of a kingdom in a cascade of defeat.  MTSgt MacDonnell’s performance was it’s opposite.  It was MacDonnell’s outstanding and innovative performance with the limited SCR-270 radar and it’s oscilloscope derived “A-Scope” that was the rock upon which victory in the air was built at Guadalcanal.  There are several books that mention MTSgt MacDonnell.  The best know naval history is John B, Lundstrom’s “The First Team and the Guadalcanal Campaign” which mentions him twice by name in the book.  The more recent “Radar and the Fighter Directors” by  David L. Boslaugh, Capt USN, Retired also mentions MacDonnell.  However the author who did best in describing what MacDonnell did at Guadalcanal was USAF historian John Kreis in his 1988 US Air Force historical monograph Air Warfare and Air Base Air Defense 1914-1973 and I’ve reproduced it below:

Pages 223, 225 and 228 


“Because the U.S. Navy was forced out of Sealark Channel around Savo Island on August 9, the Americans could not land their search radar for some days. On the day of the invasion, the 1st Marine Division had captured several Japanese radar sets that they tried to use to no avail before shipping them home to the Naval Research Laboratory. Japanese communications equipment, however, including a variety of radio and telephone components, was quickly incorporated into the alerting system. Finally, the Defense Battalion’s SCR-270B  radar was installed just before Henderson Field’s fighters arrived. Another SCR-270B went into service about  September 15. It was assigned to the Marine Air Wing’s Fighter Direction Center under control of Master Tech. Sgt. Dermott H. MacDonnell,* who became in his own right one of the keys to the air defense system on the island.”22

SCR-270B in Transport position. Source: Arthur L. Vieweger and Albert S. White, "Development of Kadar SCR-270
SCR-270B in Transport position. Source: Arthur L. Vieweger and Albert S. White, “Development of Radar SCR-270

At first the fighter control system was crude. As soon as the radar operators sighted a target, they sent
the bearing and distance to Henderson’s air operations officer, Maj. Joseph N. Renner. Lacking nearly every kind of reliable radio and signaling equipment and with almost no staff, the major launched planes as he received radar or coastwatcher reports. Later he supplemented his equipment with a salvaged aircraft radio installed in his truck. Renner also acted as an observer, identifying aircraft as friendly or enemy when they were in sight, then sounding the air raid alarm if necessary. The strain on the one man carrying  this burden was heavy.”


[* MacDonnell was born on August 16, 1921. He received the Silver Star for gallantry under fire at
Henderson. He left Guadalcanal on March 8, 1943, and returned to the United States where he was
commissioned, rising eventually to lieutenant colonel in the Marine Corps Reserve. He died in April 1976.]


On October 8, Lt. Lewis C. Mattison and Ens. W. A. Noll, both naval officers sent from the Navy’s fighter  director school at Pearl Harbor, arrived on Guadalcanal. There they found two rudimentary radar air search  operations. One was used by the 1st Marine Air Wing’s fighter controllers, the other by the 3rd Defense  Battalion. The two search efforts at first were not integrated and not always mutually supporting, although  there was contact between them. Moreover, the early radar sets were not very reliable and reported false returns from the surrounding mountains and hills. Sergeant MacDonnell was often the only man who could interpret the zigzag lines on the oscilloscopes and tell how many airplanes were in an attacking formation. Lieutenant Mattison gave much of the credit for the radar’s success to MacDonnell, who could tell from the radar set’s A-scope not only how many aircraft were in a formation, but could also frequently identify medium bombers, dive bombers, fighters, or long range seaplanes.


MacDonnell was a harried commander’s dream who specialized in getting around shortcomings in his equipment. For example, radar operators could get speed and bearings of approaching raids on the SCR-270 but had to wait for the enemy to come within 25 miles before the SCR-268 gave them the accurate altitude reading. The sergeant knew that the 270’s frame was tiltable 10 degrees backward, so that the antenna could be adjusted for terrain contour when installed. MacDonnell used this feature to take two readings on a target, one with the antenna perpendicular, another with the antenna slightly reclined. He could then calculate an approximate altitude.


Fighters vectored to the heading waited above that level. More exact determination could be made when the Japanese came within the SCR-268’s range, and the American interceptors closed in.24


Notes Page 379


20. Vandegrift Rept, Phase IV, Annex A, Phase V, Annex N; IIS No 43-8, Jan 23, 1943; Totten, Rept on Marine Antiaircraft at Guadalcanal, pp 2-5; Noll lntv; Mattison, Fighter Direction at Cactus.

21. Feldt, Coastwatchers, pp 92-96; Robert Sherrod, History of Marine Corps Aviation in World War II
(Washington, 1952), p 86.

22. Vandegrift Rept, Phase IV, Annex D,Phase III, Annex B; Rept on Radar Operation at Cactus, Master
Technical Sergeant Dermott H. MacDonnell, Dec 16, 1942, AF/CHO.

23. Noll Intv; Mattison, Fighter Direction at Cactus; Intv, author with Lewis C. Mattison, Washington, DC, Oct 7, 1983; MacDonnell, Radar at Cactus; Intv, Maj Joseph N. Renner, July 17, 1943, USAF Collection, 180.451-7.

24. Ibid.


How a Radar Echo “Jiggle” Told MTSgt MacDonnell Zeros Were Coming

In late 1942 the Imperial Japanese Navy’s A6M “Zero” Fighter was the master of the Southern Pacific skies. Between April and August 1942 the Imperial Japanese Navy’s Tainan Air Group flew 51 missions with 603 sorties and claimed 300 allied planes for the loss of 20 fighters.  It was the nursery ground of IJN aces including the redoubtable  Saburō Sakai.

The Tainan Air Group (台南海軍航空隊 Tainan Kaigun Kōkūtai) was based at Rabaul when Marines came ashore at Guadalcanal.  And, thanks to the Tainan’s experiments with aerial fuel drop tanks and the  “long of lean” fuel conservation flight methods, the 1,120 miles (1,800 km) trip from Rabaul to Guadalcanal was within the combat radius of the A6M “Zero” Fighter.

Given the technical excellence of the A6M and the combat honed skill of Tainan Air Groups pilots in August 1942.  American P-40 Kittyhawk and F4F Wildcat fighters had to to strike the highly maneuverable Zero with slashing attacks from a higher altitude with any hopes of victory.  Only excellent radar coverage and skilled fighter direction could deliver such attacks.  And by “excellent radar coverage” I mean the radar supporting Allied fighters had to give altitude, course, speed, number and type of aircraft — fighter,  single engine attack or multiple engine bombers — and it had to do this at the maximum detectable range so US Marine and US Navy F4F Wildcats had the 30 to 40 minutes they needed to climb to 30,000 Feet.  Below is an example of the cathode ray scope display that MTSgt MacDonnell sussed out most of that information.


Diagram of a typical "A-Scope" display on early WW2 Radar's. This display was derived from standard oscilloscopes
Diagram of a typical “A-Scope” display on early WW2 Radar’s. This display was derived from standard electronic oscilloscopes. 


Determining altitude, course, speed, and numbers was “normal performance” for a WW2 radar operator.  The determining altitude with the tilting of the SCR-270B’s to get a rough altitude that Kreis detailed was an outstanding and unique contribution. It would be months before the technique of determining altitude by “Fade Charts” was trained on, let alone used in the field in the Pacific.

This is the radar detection or "Fade" chart for the Type 11 Imperial Japanese Navy radar that US Marines captured on Guadalcanal. When you were tracking a plane with a radar in WW2. The range at which a plane disappeared and reappeared told you it's altitude. This fact was used extensively by US Navy shipborne radars starting in 1943 for fighter control. It was unknown to US military radar operators in 1942
This is an US Army Air Force radar detection or “Fade chart” up to 10,000 feet for the Type 11 Imperial Japanese Navy radar. One of  which US Marines captured and tried to use on Guadalcanal.  When you were tracking a plane with a radar in WW2. By following an altitude line in a fade chart above, the range at which a plane appeared, disappeared and reappeared on a radar screen told you it’s altitude.  This fact was used extensively by US Navy shipborne radars starting in 1943 for fighter direction. It was unknown to US military radar operators like MTSgt. MacDonnell in 1942.  In early 1945, Japanese Kamikaze’s started to continuously alter their altitude to successfully foil this tracking method.  Source: AFRHA microfilm reel

However, the “make or break” the air campaign genius of MTSgt  MacDonnell was that he recognized the standard aerial fighter formations of the Tainan Group GAVE OFF A UNIQUE AND IDENTIFIABLE RADAR RETURN.

IJN Shotai-Chutai-Daitai Fighter Formations Source: Sunburst: The Rise of Japanese Naval Air Power, 1909-1941

The diagram above shows the building block aerial fighter formations of the 1941-1944 Imperial Japanese Navy. The three fighter Shotai had a lead plane at lowest altitude with higher trailing planes to the left and right of the lead.  A Chutai was three Shotai (nine planes) in a similar orientation and a Daitai was three Chutai (27 planes).

Each trailing plane behind a lead plane, or trailing element behind a lead element, did not keep a tight formation position.  They drifted and winged back and forth looking for enemy planes. They did this for a reason. The IJN Shotai-Chutai-Daitai Fighter Formations Fighter Formations were visual communications based.  The IJN fighters of 1941-1944 had unreliable high frequency radios that could not be counted upon to work in combat. Point in fact, even if the IJN did have a reliable radio design in that period. Japan simply lacked the vacuum tube electronics production capability build them in the numbers required.

In the offensive, with well trained pilots who had worked together, the Shotai-Chutai-Daitai Fighter Formations were a formidable system of defense in the event of surprise attack for defending enemy fighters.  They were less well suited to escorting bombers or to the point defense of a carrier or air base.  As a radio call was the best way for an defending/escorting fighter to be vectored to the enemy if your plane is banked away from the attack, scanning a different part of the sky.

All of this back and forth positioning and scanning made the Shotai-Chutai-Daitai  “formation” look more like an unorganized cloud of bees to Allied fighter pilots who were used to the tight three plane “Vic” of pre-war tactics.  That is, until they attacked a Chutai or Daitai and all the Shotai’s broke into line-a-beast or line-a-stern tightly turning elements to eat the Allied pilots live.

However, to the keen eye and sharp mind of MTSgt MacDonnell looking at his A-Scope.  The radar echo of the Shotai-Chutai-Daitai Fighter Formations were unmistakable.  The echo “jiggled” as different Zeros in their formations showed different portions of their airframes constantly increasing and decreasing their radar reflections.  However the Imperial Japanese Navy mixed their planes, the radar return of the Shotai-Chutai-Daitai Fighter Formations gave away to MacDonnell where the Zeros were…or were not.

MTSgt MaDonnel Did not work alone. This is the MAG-23 headquarters Squadron Radar Crew on Guadalcanal. Source USMC History Archives, courtesy MACCS History
MTSgt MacDonnel did not work alone. This is the MAG-23 headquarters Squadron Radar Crew on Guadalcanal.  MacDonnell’s crew included  PFC W. S. Taylor, and eight privates, H. D. Nichols, Robert W. Schultz, Julius W. Jones. W. M. Yurillo, C. L. Dill, G. F. Dolan, H. M. Wooley and Franklin T. Rainier. Source USMC History Archives, courtesy MACCS History

The following is clipped from a document titled “Confidential notes on the maintenance and operation of SCR-270, compilation of,” and is dated 7 October 1943.  It details the radar echo “identification templates” MacDonnell  recognized in the course of Imperial Japanese Naval Air Force’s raids on Henderson Field.

Page 2 of "Confidential notes on the maintenance and operation of SCR-270, compilation of," dated 7 October 1943. source USMC History Archives, courtesy of MACCS History
Page 2 of “Confidential notes on the maintenance and operation of SCR-270, compilation of,” dated 7 October 1943. Source: USMC History Archives, courtesy of MACCS History

MTSgt MacDonnell’s “echo templates” were based on speed, altitude and “jiggle.”   High altitude at 180 knots air speed, that was a Betty bomber.  Medium or high altitude at 200 kts, those were single engine dive bombers.  If the echo was at any altitude at 250 kts and it “jiggled”, it was a Zero fighter sweep.  If either the 180 kt. or 200 kt echo “jiggled” you were looking at fighter escorted bomber formations.

MacDonnell’s Last & Undocumented Radar Math Trick

MTSgt MacDonnell had one final trick to extract the maximum range from his SCR-270B radar based upon the geography of the Solomon’s Campaign.  One that wasn’t documented for reasons I’ll touch on a little later. First, look at the map below.

Solomans Campaign Map from a 1993 issue of Naval Aviation News.
Solomons Campaign Map from the Nov/Dec 1993 issue of Naval Aviation News.

The Rabaul based Tainan Air Group was operating at the ragged edge of it’s 600 mile maximum combat radius range over Henderson Field.  Tainan’s Zeros quite literally had to fight over Henderson Field while retaining their drop tanks in order to have enough fuel to get back to Rabaul.  Reports from Australian Coast Watchers and MacDonnell’s own radar showed the Japanese used the exact same air route every time because of that range limit.  Being a man well versed with math, as his radar antenna trick showed, it was very simple for MacDonnell to calculate the earliest time a Japanese raid could appear at the maximum range of his radar based upon which coast watcher station radioed in. So a few minutes before this was to happen and until the raid appeared.  MTSgt MacDonnell “sector scanned” his SCR-270B radar through a 30 to 60 degree sector (smaller earlier, wider later) until he picked up the incoming raid.  Then he paused the radar antenna right on top of  the strongest echo return to take a pair of slant range measurements to calculate altitude.

This gave an approximate altitude at over 100 and up to 120 miles range, until the incoming Japanese air raid came into the 20-to-30 mile range of the SCR-268 search light radars directing the Marine’s 3rd Defense Defense Battalion’s 90 mm guns.  The SCR-268 radars were designed from the start to give an altitude within 200 yards and their tracking of the raid gave Cactus fighter direction the exact altitude to bring down their F4F Wildcats to best advantage.

The Role & Mission Politics Which Saw That the “Horseshoe Nail of Victory” Was Forgotten

The impact of the highly classified after action reports of Cactus air operations officer Maj. Joseph N. Renner,  Cactus chief fighter director officer Lt. Lewis C. Mattison  and MTSgt MacDonnell created a sensation.  MacDonnell’s radar echo identification templates became the basis of training of all Marine and Naval SCR-270 radar operators deployed to the Pacific in World War 2.

This is the cover page of "Confidential notes on the maintenance and operation of SCR-270, compilation of," dated 7 October 1943. The 1st Marine Aiw Warning Group was the primary radar training organization for the USMC in WW2.
This is the cover page of “Confidential notes on the maintenance and operation of SCR-270, compilation of,” dated 7 October 1943. The 1st Marine Air Warning Group was the primary radar training organization for the USMC in WW2.

The US Army Signal Corps, whose SCR-270 radar was unfairly blamed for Pearl Harbor by the US Army Air Force, quickly modified the SCR-270’s antenna tilt system for the Ground Control Intercept (GCI) role in the proposed SCR-289, SCR-530 and SCR-531 radars.  The USAAF refused and chose the fixed and mobile versions of the RAF AMES Type 7 GCI radar.  Which were built as “Reverse Lend Lease” in Canada as the SCR-527 (Mobile) and SCR-588 (Fixed) GCI radars.  As Canadian production and shipping shortages meant there were not enough SCR-527 & SCR-588 available for North Africa in late 1942-to-mid 1943. The Signals Corps also adapted the SCR-268 search light radar based on Australian modifications that added a new plan position indicator (PPI) indicator in addition to the “A-Scope” to become the visually identical SCR-516 GCI height finding radar. Which the USAAF did accept as a stop gap, because it had no choice.

USMC 3rd Defense Battalion operated SCR-286 at Henderson Field
USMC 3rd Defense Battalion operated SCR-286 Searchlight radar at Henderson Field. It was visually identical to the later SCR-516.  Source: Pacific Eagle’s web site

Meanwhile, in the on-going Solomons campaign, the theater commander Adm. Halsey faced a horrid radar supply situation. The land based radars he needed were built by the War Department and the War Department’s first priority was fighting Germany.  And the aforementioned North African Campaign meant none were available.  Also, in the back ground, there was a multi-service and multi-faction roles and missions battle happening over who would control radar both in the South Pacific Theater and in the United States.

Adm. Halsey had to make due with what he could get locally. And what he had locally was New Zealand.  New Zealand had been let in on the UK radar secret in 1939 and had created a line of radars that were being used locally to protect New Zealand’s territory. During 1942-43, the New Zealand Radio Development Laboratory (RDL) was organized over both radar production and New Zealand’s radar production facilities and made the US Navy aware of its capabilities, trying to drum up orders and political visibility. Under the political terms creating the South Pacific theater  Halsey could, and did, demand these radars be sent to the Solomon’s to support the campaign there, much to the chagrin of the New Zealand government and military high command.

The first radar to arrive from New Zealand was with Radar Detachment no. 52. a “Ground Control Intercept” or “G.C.I.” radar unit that could determine aircraft altitude — which the American SCR-270 radar could not — and direct radar equipped night fighters. It arrived the same month that MTSgt. MacDonnell left Guadalcanal.  This is what the Royal New Zealand Air Force (RNZAF) official history says about Radar Detachment no. 52.

The New Zealand GCI set was the first of its kind in the South Pacific. For the first two days after the Americans had landed on Guadalcanal in August 1942, fighter direction had been carried out from the USS Chicago and fighter cover had been flown from the carriers Saratoga and Enterprise. When the ships withdrew from the area the Americans had neither fighters nor radar.


By 20 August F4Fs and SBDs were based at Henderson Field, but no adequate provision had been made for fighter direction. A search radar model SCR 270-B was put into operation in September and was used for the purpose. The type was satisfactory in giving warning of the approach of hostile planes but was not suitable for plotting heights and tracks accurately, so that the American pilots in the air could seldom be vectored exactly on to the enemy. This limitation was more apparent after the middle of November when the Japanese began frequent night raids. For night-fighter control the SCR 270-B was inadequate.


The arrival of the RNZAF unit in March 1943, therefore, filled an important gap in Guadalcanal’s defences. The GCI set could give the accurate readings, particularly in altitude, which were necessary for night interceptions. The set was operated by RNZAF personnel; and United States Army, Navy and Marine, as well as New Zealand, controllers directed the fighters. None of the controllers had had combat experience with GCI, and results in the first month of operations bore out Major Best’s contention that a period of training in New Zealand for both controllers and pilots should have been arranged.

After this troubled debut, the RNZAF proceeded to distinguish itself with its radars and trained radar crews in the Solomons.  Adm Halsey proceeded to play patron to a series of new US Navy ground based radar units called “ARGUS,” which  used a combination of dismounted US Navy Destroyer radars adapted to ground mounts and New Zealand RDL designed and built radars.  ARGUS units were essentially a US Navy fighter direction combat information center on shore which conformed in every way with US Navy afloat radar doctrine.

In the mean time, there was a roles and missions fight between Marine Aviation and Marine defense battalion advocates over who should control land based radars supporting Marine Aviation.  This was resolved in favor of Marine Aviation, but the after action reports from the Solomons showed that radars had to be separated from Marine Air Groups.  Radars were simply too heavy and too necessary to the operation of an air base to keep up with a Marine Air Group relocating to a new base.  This resulted in the creation of Marine Air Warning Squadrons (AWS) in 1943.

This is the MAG-23 SCR-270 radar in position on Guadalcanal. There was an identical 3rd Marine Defense Battalion SCR-270 on Guadalcanal as well. There was very little coordination between the two radars for most of the time MTSgt MacDonnell was on Guadalcanal.
This is the MAG-23 SCR-270 radar in position on Guadalcanal. There was an identical 3rd Marine Defense Battalion SCR-270 supporting 90mm AA guns on Guadalcanal as well. There was very little coordination of reports between the two radars for most of the time MTSgt MacDonnell was on Guadalcanal. This duplication of effort was the source of  later USMC organizational controversy. Photo Source: MACCS History

The problem was the Marine AWS competed directly for the same role and mission as the US Navy Argus units. And Admiral Halsey, as the patron of the Argus units, was not a man to be denied.  Fortunately for the US Marine Corps, power politics intervened between the US Navy on one hand and both Australia and New Zealand on the other and the fall out from this political conflict shifted the balance in favor of the USMC AWS.  [See my January 3rd, 2014 column “History Friday: Admiral Nimitz’s Kiwi Radars & Power Politics in the South Pacific” for the details.]

It was these Marine Aviation roles and missions conflicts where things went sideways in terms of the public memory of MTSgt MacDonnell’s role in the Guadalcanal campaign.

Commandant Vandegrift’s War to Save Marine Aviation

General Alexander Archer Vandegrift was the commander of the 1st Marine Division on Guadalcanal.  He was chosen in 1943 by out-going Marine Commandant Thomas Holcomb as his replacement, not to help win the war, but to make sure the USMC survived the impending unification of the War and Navy Departments into a unified “Department of Defense.”

The key to the USMC’s survival in a unified Department of Defense was keeping USMC Aviation.  The Marine Corps shorn of it’s Fighter Wings was just another ground unit. Which in time would be swallowed as a Corps sized unit inside the US Army via Congressional budget cutting.  For the USMC to survive, Commandant Vandegrift had to be utterly ruthless inside the Corps and Navy Department to fit Marine Air into the Navy’s current and post war plans.

The three legs of Vandegrift’s plans were a reduced AWS program which went from 32 squadrons to less than 16.  The placing of  Marine fighter squadrons on US Navy escort carriers (CVE) and a focus on Close Air Support (CAS) as the signature USMC aviation specialty as a part of a “Marine Air Ground Task Force.” USMC Commandant Vandegrift canned the previous Commandant’s Chief of Aviation and sent him on a military mission to Argentina so he would gets someone who was sufficiently focused on Marine Aviation performing CAS from US Navy escort carriers.

Then in late 1944, as Commandant Vandegrift had predicted, the elimination of Marine Aviation was to be at the center of the initial DoD roles and missions war.  The testimony in December 1944 at Oahu, Hawaii to a Congressional committee (which was examining the creation of a post-war Defense Department) by Pacific Ocean Area’s (POA) ranking US Army General — General  Richardson —  was the first shot of that turf fight. This testimony was a seminal event inside the US Military in that it affected war plans for Iwo Jima, Okinawa and the planned invasion of Japan plus it was the initial “Flaming Datum” of the bureaucratic wars that lead up to the “Revolt of the Admirals.”

The text passage from General Richardson's December 1944 testimony on Marine Aviation to the Congressional Committee on Defense Unification
The text passage from General Richardson’s December 1944 testimony on Marine Aviation to the Congressional Committee on Defense Unification, Source: MacArthur microfilm collection, MacArthur Memorial Holdings, Norfolk, VA

This late 1940’s USMC survival struggle saw Commandant Vandegrift sacrifice the classified exploits of MTSgt McDonnell for the sake of a military service brand that was central to the USMC’s survival.  Namely, the brand that the USMC did not do factions.  Every marine was a rifleman.  The Marines made due and did more with less.  And in the end, that it was the Marines and US Navy versus the world.

In truth, none of that was -fully- true.  It was the USMC versus the world. Period.  But to keep the brand,  MTSgt MacDonnell’s exploits were never given the attention they deserved.  And this is where the point about his sector scanning comes in.

When Commandant Vandegrift had the Marine AWS units take on the ARGUS role and mission.  He had to adopt US Naval screen doctrine that came with it. This doctrine reflected the failure of the of US Navy screening Destroyers in the First Battle of Savo Island to keep watch astern.  Where Vice Admiral Gunichi Mikawa’s task force passed behind a screening destroyer to slaughter four allied heavy cruisers.

Radar sector screening, as opposed to continual 360 degree air/sea watch, was a standard practice of Allied and Axis land based radars.  This was driven by echos from land terrain and enemy air base location making some air approaches more likely than others.  Additionally, land based radars operated as networks in a way screening US Navy ships did not.

After Savo Island,  the US Navy simply was not going to listen to any of it.  Screening units looked in every direction. Period.  So the AWS units were careful never to mention this standard land radar tactic from 1943 onward. This made celebrating MTSgt. MacDonnell’s radar genius at Guadalcanal…problematic.  So into the memory hole he went.

Until now.




P.S.  Special thanks here to Mark Murphy, “MACCS History” who has kept the torch of the Marine Aviation Command and Control System history alive. His work made this article on MTSgt and later LTC Dermott H. MacDonnell, one of the MACCS community founders,  possible.


P.P.S  Please note in the photo below that the USMC officially recognized MTSgt Dermott H. MacDonnell’s role in saving Guadalcanal.

Major Gen. Roy Geiger (Center) awarding Navy Cross to Col Cooley (far Left) and Silver Star to MTSgt Dermott H. MacDonnell (2nd from the Left)
Major Gen. Roy Geiger (Center) awarding Navy Cross to Col Cooley (far Left) and Silver Star to MTSgt Dermott H. MacDonnell (2nd from the Left)  Source: MACCS History


Sources and Notes:

David L. Boslaugh, Capt USN, Retired, Radar and the Fighter Directors
Friday, October 30, 2015

FTP 217, U.S. Radar, Operational Characteristics of Radar Classified by Tactical Application,
Prepared by Authority of the Joint Chiefs of Staff, by the Radar Research and Development Sub-Committee of the Joint Committee on New Weapons and Equipment, 1 AUGUST 1943

John F. Kreis, Air Warfare and Air Base Air Defense 1914-1973 Office of Air Force History United States Air Force Washington. D. C. 1988 ISBN 0-912799-55-2, Pages 223, 225 and 228

Lundstrom, John B., The First Team and the Guadalcanal Campaign, Annapolis, MD, Naval Institute Press, 2005, ISBN 978-1-59114-472-4. (Lundstrom 2005, -2),  Page 237, 266

Radar Descriptions
MPQ – Mobile; Radar; Special

Royal New Zealand Air Force, CHAPTER 15 — Radar Units in the Pacific, Dispatch of No.52 Radar Unit to Guadalcanal, © 2013 Victoria University of Wellington, accessed 1/01/2014 

Frank Shaw, History of the US Marine corps Operation in World War II, Victory and Occupation, Histoprical Branch, g-3 Division, Headquarters, USMC (USMC Escort Carrier Operations pages 410 – 429)

Trent Telenko, “History Friday: Admiral Nimitz’s Kiwi Radars & Power Politics in the South Pacific”
January 3rd, 2014

USN Argus Unit Historical Group

Arthur L. Vieweger and Albert S. White, “Development of Radar SCR-270”C&E Digest. (November 1959) HQ Air Defense Command Directorate of Communications-Electronics.

C. F. WAYHAM, 1st Lt., Sig C, Ground Communications Division, Communications Department, RADAR (200-5-7-1),  Army Air Force School of Applied Tactics, March 1944, Call Number N5269.16


39 thoughts on “The Guadalcanal Air Campaign’s “Horseshoe Nail of Victory””

  1. I did not know all that about radar on Guadalcanal. Thanks, it was very informative.

    Not related to radar but does touch on some of the other stuff, let me give a big shout out to WEB Griffin. I just read the entire The Corps series again for the umpteenth time. Guadalcanal is front and center in a couple of the books.

    They never get old.

    Except for the last 2 Korean War books. Not terrible but not worth rereading.

    John Henry

  2. In the Army decades ago, I was in Air Defense. And as a fallback during NATO exercises I would plot “enemy aircraft” on a Plexiglas board and call out the positions to various missile batteries and “friendly” pilots.

    But this guy went way beyond that.

    An unsung hero.

    A bit of Guadalcanal family trivia: I had 2 relatives (distant uncles I believe) – 1 a Marine aviator, the other a Marine infantry officer, who met each other at the O-Club at Guadalcanal – neither knew the other was there until that meeting.

    I am certain the aviator knew all about MacDonnel.

    Knowledge is is a major factor in battle, and he gave it to them.

    I wonder how much difference Pearl Harbor would have been if the right people had listened to that air defense station on Oahu.

    But it was a different mindset.

  3. The post has had numerous small edits for spelling and grammar and the addition of a photo clip showing a small text passage from General Richardson’s December 1944 testimony on Oahu, HI.

  4. >>Any idea what’d he do with the rest of his life?

    Beyond what was in Kreis’, no.

    Internet searches turn up zip.

  5. Well, from his Silver Star commendation ( we see that his middle initial was H and he’s from Lawrence, MA.

    This obituary appears to probably be his daughter?:
    “Ms. MacDonnell was the daughter of the late Dermott H. MacDonnell of and the late Margaret J. Noggle from Amherst MA.”

    This is probably him?: (died in 1976)

    I don’t see any sign of an obit for him or his wife online.

    Amazing that someone could make such a contribution and then just disappear. That’s America, I guess. Probably if he’d lived another few decades someone would have made more of a big deal about his death, but no one in the mid 70s was keeping track of WWII vets passing away young…

  6. I did some quick internet searching, my comment appears to have been swallowed up by the system, rather than retype it and have it duplicate in case the original shows up, it looks like he died in 1976, had several children, no signs of an obit that would say anything about what he did with the rest of his life…

  7. MacDonnel ended up staying in the Marine Corps. He received his commission and after instructing radar at MCAS Cherry Point for a year became a fighter director with Air Warning Squadron 6 during the Battle if Okinawa. He also served as a company commander with The 1st Reconnaissance Battalion during the Korean War and served with great distinction. He retired around 1963.

  8. Two tidbits jumped out as intriguing surprises in the context of some of Trent’s essays over the last year:

    1) The Japanese use of drop tanks (wonder what they were made of). Recall that later in the war these made the difference for the P47 and P51 in Europe.

    2) The Japanese adopting the practice of lean mixture. Recall Lindbergh recommending this for American fighters even though it makes engine temperature increase. Tho this at minimum reduced engine life and could if even a little too lean quickly destroy an engine, careful use of slightly lean mixture can significantly increase range. Lindbergh correctly observed that in the scheme of things replacing engines was a wise, affordable trade-off for gaining the airspace control longer range enabled.

    Meanwhile, the Zero’s reason for existence demanded nearly the opposite practice. Japan did not have enough access to metals that would enable making large quantities of alloys needed for engines both light weight and able to withstand higher tempertures. To offset the extra weight of the only engine Japan could make, Zero’s designer took off weight elsewhere, namely less armor and less structural support. Terrible trade off, since while it made the Zero able to out climb and out turn Allied aircraft early in the war, it also meant that the Zero from nearly the beginning of the war was “fragile” in comparison to the aircraft it could outperform. To run the Zero’s engine on the lean side meant a much more serious risk of engine damage than it did for the U.S. planes. And Japan did not have the wealth for engine replacement that the U.S. did.

  9. at least two of web griffin’s series, the marine one, and the honor one, with future col, frede of the company,

  10. Dermott H. MacDonnell is my father. He died April 10, 1976 in Northampton, MA and buried in Lawrence, MA. He married my mother Margaret J. Noggle in Washington DC in March, 1946. Their first two kids (I am the oldest, the second born Kathleen died in 2007) were born at Bethesda Naval Hospital and from their they moved to Camp Lejeune. When my dad was deployed during the Korean War, the family moved to San Diego to wait for him, and then we moved to New Rochelle, NY. In 1957 he was deployed to Guantanamo Bay, Cuba as the executive officer shortly after Fidel Castro had taken over the country. In 1959 we moved to the air station at Santa Ana, CA and were there for a two and a half years, until his retirement from USMC in 1962. We moved in December that year to Burlington, MA where dad and a veteran colleague began a company working with electronics and weaponry for the US government. During that period he also got me to join the US Navy Nurse Corps and was the one to swear me in – I served from 1967 – 1972. Like many of the companies in the Boston area, once the Vietnam War wound down, Dad’s company folded in the early 1970s and he went into full retirement mode and moved with my mother to Amherst MA. He died at the Northampton VA hospital.

  11. A friend of mine, I dated his daughter for a time, flew Corsairs from Guadalcanal, but in 1943. He also flew them in Korea. His son and two grandsons were Marine fighter pilots. The son flew in Desert Storm, one grandson flys an Apache and the other grandson is still at Pensacola.

  12. Great column. But you have to give it to the Japanese fighter pilots. Its amazing they did as well as they did, given they had to fly 600 miles one-way and engage an enemy that always knew they were coming.

    And also give credit to the Japanese admirals who understood the importance of RANGE better than there American counterparts. You have to wonder why Drop Tanks took so long to be adopted by the US Navy, and why they weren’t included in the original design of Navy fighters. After all, the Carrier that got in the first lick, usually won.

    Of course, this off-topic. I can’t say much about MacDonnel, there were a lot of unsung heroes who came up with weapons or techniques that allowed us to win the war.

  13. Everyone give Mark Murphy a round of virtual applause.

    As “MACCS History” he has worked for 6-years building a Facebook community and gathering the stories of the USMC aviation radar command and control community.

    His sharing of some of that work made this post possible.

  14. Note: There was a slight edit to the article to add the names of MTSgt MacDonnell’s radar crew under their group photo. (Thanks Mark!)

    Sadly, I can’t tell you which men are who.

  15. Rcocean,

    Imperial Japanese Navy land based airpower doctrine was far in advance of the RAF/RN & USN/USMC equivalents in 1941-1943.

    The performance of the Tainan Air Group in the first year of the war and the sinking of the Prince of Wales and the Repulse off Malaya reflected that fact.

    Consider, the Zero flew a 600 mile range in 1942 with one 73 gallon belly tank that the P-51 with two 75-gallon wing tanks did not match until March 1944.

  16. The internet can be an amazing thing. This great article prompted my random musings about the subject and in less than a day his daughter appears to answer the question. Wow.
    Mrs. Holmes, thank you.

  17. With your permission I would like to share this with the National Electronics Museum in Linthicum MD ( They have an SCR-270 on display and this story would add to the store of information there. It is a fascinating story and one I had not come across either in my history readings or my 40+ year career developing radar systems at Westinghouse (the manufacturer of the SCR-270) and later Northrop Grumman (who acquired Westinghouse Defense in 1996).

  18. Mr Fisher,

    As long as you credit me and the Chicagoboyz blog, spread this story as far as you wish.

    However, I’m curious as to what was new to you in this story.

    Kreis’ work speaking about MTSgt. MacDonnell has been around since 1988.

    Lt. Lewis C. Mattison’s report speaking about MTSgt. MacDonnell is mainstream US Naval history via Lundstrom’s “The First Team and the Guadalcanal Campaign” which is almost as old.

    The only two things I’ve added is explaining the how MTSgt. MacDonnell did what he did via “Confidential notes on the maintenance and operation of SCR-270, compilation of,” and putting together why his performance got buried via General Richardson and Commandant Vandegrift.

    The sad thing for me in all this is that there is no way Academic Military Historians will go near this story because it involves a lot of higher math and non-Newtonian physics.

  19. “a lot of higher math and non-Newtonian physics.”

    Don’t understand…estimating altitude for the antenna angle giving the strongest signal would seem like a matter of basic trigonometry.

    (of course, that might *seem* like higher math for a lot of historians…)

  20. David,

    Higher math = “anything more advanced than addition and subtraction.”

    Academic military historians got into history because they didn’t want to do math.

    When you start talking about frequency, wavelength, trigonometry, circuit structure, quartz crystal control, atmospheric transmissiblity and radio ducting, they fragging run for the hills.

    If you put all of the above in terms of everyday technology they are familiar with — I use television — you can keep them from running, but they are skittish and uncomfortable as all h**l.

    This is why the published histories of the Okinawa campaign in WW2 are so horrid. The real story of the battle of Okinawa involved all of the above. Which, boiled down, the Japanese were winning the fight for the electromagnetic spectrum from late March through late May 1945 because the US Navy wasn’t paying attention.

    Junior to field grade Naval and Marine officers figured out what was going on by mid-April 1945, particularly the electronic warfare officer on the amphibious command ship USS Estes.

    It wasn’t until Adm Turner got a radio-intelligence unit of his own in late April 1945 that things began to improve. AKA Adm.Turner listened to his new radio intelligence unit, not his junior officers.

    But it wasn’t until late May with the USMC ground based radar network finally being in-place and an additional _and competent_ Marine night fighter squadron being brought in that Japanese night time air superiority over Okinawa could be really contested.

    It finally took the 6th Marine Division over running Adm Midoro Ota’s IJN Naval headquarters in Naha — and it’s under sea cable facilities connected to Formosa — for the US Navy to seal the deal on night time air superiority over Okinawa.

  21. Mark,

    This was where I got the Commandant Holcomb background for this article I wrote on MTSgt MacDonnell.

    Preparing for Victory” by Dr. David J. Ulbrich
    Published on Jul 24, 2014

    The video above is for this book:

    Preparing for Victory: Thomas Holcomb and the Making of the Modern Marine Corps, 1936-1943 (Leatherneck Original) Kindle Edition
    by David Ulbrich (Author), Colonel Charles P. Neimeyer USMC (Ret.) (Foreword)

    The Marine Corps does not hide the exploits of it’s heros from it’s members unless it is a dire survival issue.

    And that is exactly what Commandant Vandegrift faced in 1943.

  22. Out of curiosity, I went back to see how many Chicagoboyz post’s I’ve done on the use of Radar in the the Pacific theater of WW2.

    This is the list:

    RADAR IN THE PACIFIC WAR 1941 – 1945

    The Guadalcanal Air Campaign’s “Horseshoe Nail of Victory”
    Posted by Trent Telenko on May 19th, 2019

    History Weekend — The Darwin Air Campaign’s “End of the Beginning”, Plus 75 Years
    Posted by Trent Telenko on 16th September 2017

    Pearl Harbor, December 7th 1941 — Plus 75 Years
    Posted by Trent Telenko on 7th December 2016

    History Friday — Imperial Japan’s Philippine Radar Network 1944-45
    Posted by Trent Telenko on 10th June 2016

    Operation Chronicle and Airspace Control in the South West Pacific
    Posted by Trent Telenko on 25th April 2014

    History Friday: Unit Conversion Error in the Pacific War
    Posted by Trent Telenko on 4th April 2014

    History Friday: Admiral Nimitz’s Kiwi Radars & Power Politics in the South Pacific
    Posted by Trent Telenko on 3rd January 2014

    History Friday — MacArthur’s Anglo-Australian Radars
    Posted by Trent Telenko on 28th June 2013

    Pearl Harbor Plus 71…a Matter of Minutes
    Posted by Trent Telenko on 7th December 2012

  23. Trent,
    I know that the museum has little or no information on the use of the SCR-270 at Guadalcanal. Also, to the best of my knowledge, the museum does not have any of the technical detail shared here on the ‘tricks’ MTSgt. MacDonnell came up with to get more from the radar than its designers intended. I certainly hadn’t seen it; maybe now that I am retired I will have some more time to spend on this kind of historical detail. I also agree that traditional historians’ eyes will glaze over at the technical detail. The Electronics Museum has some serious geeks that support it. I’m sure they will be interested. Thanks again!

  24. Regards this —

    >>I know that the museum has little or no information on the use of the SCR-270 at Guadalcanal.

    Mark Murphy (AKA MACCS History) was my source for “Confidential notes on the maintenance and operation of SCR-270, compilation of,” dated 7 October 1943.

    If you e-mail my Trent_Telenko -at- account I can forward you a copy.

    However, there is a wealth of WW2 radar operational data and doctrine your museum can mine fior your WW2 exhibits at the US Army’s Ike Skelton Combined Arms Research Library Digital Library.

    Over all “CARL DL” Link:

    World War II Operational Documents

    “Radar” as a search term at World War II Operational Documents

    “AAF School of Applied Tactics” as a search term World War II Operational Documents:

    Check it out.

  25. There were three edits to the post.

    The first is a USAAF technical intelligence fade chart of the IJN Type 11 radar Marine captured on Guadalcanal.

    The second is a photograph of the SCR-270 Radar MTSgt MacDonnell used on Guadalcanal and the third edit is a photograph of is of Major Gen. Roy Geiger giving the silver star to MTSgt MacDonnell for his performance.

    Both photos are the courtesy of MACCS History.

  26. I was watching ‘in harms way’ which was an otto Preminger film with john wayne and kirk douglas, based on a novel by james bassett about that critical span from pearl harbor to the Solomon campaigns, a very unglamorous look at the navy in a time when victory was by no means certain,

  27. yes it seems plausible, of course bassett (i’m assuming Preminger, stayed faithful to that plot point,) killed off commander eddington, at the battle of what appears to be Guadalcanal, good intel officers do not get their best rewards, add Rochefort to that list,

  28. I read the book before seeing the movie and I should have said that the author seemed to use Browning as his model of the hard bitten CofC.

    The sex plot was, of course Hollywood. The Wayne role was not based on Halsey as I recall.

  29. “In Harm’s Way” was a piece of anti-MacArthur propaganda in that MacArthur’s SWPA never had a higher military priority than the South Pacific.

    King/Nimitz/Halsey routinely stole planes, rockets and lighterage (AKA tugs, barges and beach cranes) from MacArthur’s freighters on the way to Australia.

    They never got around to stealing MacArthur’s Higgen’s boats or trucks as MacArthur had them shipped knocked down (a lot of assembly required) to save freighter space.

    MacArthur had a factory each for trucks and Higgens boats in Australia to reassemble them.

  30. well I didn’t garner that particular angle, but that seems about right, intra service rivalries can be as vicious as that with foreign powers, stephensons cryptonomicon shows a certain marine distaste for macarthur and even a veiled swipe at then lieutenant Reagan,

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