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.”
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.”
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.
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.
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
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
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