Today’s History Friday column is another in a series focusing on an almost unknown series of military documents from World War II (WW2) called “The Reports of the Pacific Warfare Board,” and specifically Pacific Warfare Board (PWB) Report #35 Armor Vest, T62E1 and Armor Vest T64. (See photo below) This report, like most of the PWB reports, had been classified for decades and only now thanks to the cratering costs USB flash drives and increasing quality of digital cameras has it become possible for the interested hobbyist or blogger to access and write about these reports from the formally hard to use National Archives. And PWB #35 is about one of those hugely important but overlooked details — Infantry Body Armor — that utterly undermine the established historical narratives by the professional Military history community about the end of WW2 in the Pacific. Namely that the Japanese would so bloody attacking American invasion forces the Japanese would “win” – for values of winning – a more favorable settlement of the war.
According to PWB #35, both the T62E1 and T64 vest (the latter is pictured above and was standardized as the M12 in August 1945) were sent for combat testing to MacArthur’s 6th and 8th Army’s in the Philippines in June and July 1945. The T64 vest was chosen for series production as the M12 in the summer of 1945 with 100,000 supposed to be finished by the end of August. This was sufficient time to ship those vest to the Pacific for all the assault infantry regiments participating the cancelled by A-bomb invasion of Japan, code named Operation Olympic.
Why infantry body armor like the M12 is so disruptive for the established narratives boils down to one word — casualties. The deployment of 100,000 such vests would have reduced American infantry casualty rates from lethal artillery fragments in the invasion of Japan to roughly Vietnam levels. This means roughly 1/3 fewer combat deaths from artillery fragments and about an overall 10% to 20% reduction in total projected combat deaths. Depending on which of the historical casualty ratios you select for measurement, it means something on the order of up to 10,000 fewer battle deaths, in the event that the A-bomb hadn’t made the invasion superfluous.
I would call this a very significant, reality altering, detail.
When you do internet searches on this T64/M12 body armor, there is a wealth of detail on line, with the two biggest hits are Osprey Publishing’s “Flak Jackets – 20th-century military body armour,” by Simon Dunstan and the on-line version of WOUND BALLISTICS, by the US Army Medical Department’s Office of Medical History. The former used much of the latter verbatim, so I will take WOUND BALLISTICS as definitive. The following is from page 737, the on-line chapter 12, of WOUND BALLISTICS regards the effectiveness of the Korean War vest T-51-2 (also pictured below):
“These studies indicate that 30 to 40 percent of the fatal chest wounds incurred by soldiers in combat would have been prevented by the use of body armor. From another point of view, this seems to indicate that 10 to 20 percent of the soldiers who were killed in action would have survived if they had worn body armor. The effectiveness of the vest in preventing chest wounds in the KIA casualties was not so marked as in the WIA casualties. One explanation of this disparity lies in the higher incidence of small arms wounds in the KIA (approximately 25 percent) as compared to the WIA casualties (approximately 15 percent).
Pictured below are the various artillery and bullet fragments picked out of the six pound Korean War vest T-51-2
Too make things even more interesting, the same internet search that found the above information also found a hobbyist the US Militaria forum has actually built a simulation of the M12 vest and fired ammo at it. His results suggest that a 12 pound M12 vest might have been rated as high as “Level IIIA” in some places (stops most moderately powered pistol rounds). See the link:
CRUNCHING THE IWO JIMA NUMBERS
To baseline what the difference the M12 vest would have made for the invasion of Japan, I pulled a pair of military medical reports on Iwo Jima — one a March 1945 US Army report and one post war US Navy (See notes) — to crunch numbers. The USMC Assault infantry regiments suffered 75% casualties of initial strength over the course of the Iwo Jima battle. The supporting regiments took 60% casualties.
What is interesting here is that in terms of “Casualties per thousand per day,” the military-medical standard measurement of casualties. Iwo Jima was much less bloody in terms of casualties per 1000 per day than Tarawa, at 12.74 versus Tarawa’s 80.55 per 1000. And more surprising still, the USMC assault with the highest casualty rate for the first day was Saipan, at 100 casualties per 1000.
The difference between either Tarawa or Saipan and Iwo Jima was time. Tarawa was three days long. The assault on Iwo Jima was 26 days.
In terms of battle deaths on Iwo Jima, there were 5,460 dead, 22% whom died of wounds after getting to medical treatment. Had the M12 been available to the Iwo Jima Marines, we are looking at 546 to 1092 more Marines surviving the battle, using the Korea war data for a less well armored T-51-2 vest…and the M12 vest was much more protective!
Now you all have a better idea why I think the arrival of the digital age is undermining past historical narratives.
Notes and Sources —
1. Major JAMES C. BEYER, MC, ed. “MEDICAL DEPARTMENT, UNITED STATES ARMY, WOUND BALLISTICS” OFFICE OF THE SURGEON GENERAL DEPARTMENT OF THE ARMY WASHINGTON, D.C., 1962
o CHAPTER XI Personnel Protective Armor
o Chapter XII Wound Ballistics and Body Armor in Korea
2. C.G. Blood, Report No. 90-16, “SHIPBOARD AND GROUND TROOP CASUALTY RATES AMONG NAVY AND MARINE CORPS PERSONNEL DURING WORLD WAR II OPERATIONS,” Naval Health Research Center, Medical Decisions Support Department, P.O. Box 85122, San Diego, CA 92186-5122
3. Simon Dunstan, Men-at-Arms 157, “Flak Jackets – 20th-century military body armour,” Osprey Publishing, June 1984; ISBN: 9780850455694
4. Captains Charles F. Koser and Daniel Prettyman, US Army Medical Corps, “The Iwo Jima Operation (19 February to 16 March 1945),” March 1945, N-18600.1-E, CGSC Ft. Leavenworth, Kan. DTIC Accession Number ADB308635 Page 4
5. Pacific Warfare Board Report #35, NARA