A snippet of the relevant part.
Given the overwhelming majority of deaths were caused by artillery fragments, I can see this saving many lives. Of course as noted in the article the arm protection likely would have gone away do to the need to smoothly operate the bolt of the current rifles of the era but machine gunners would likely have kept them.Enter Bashford Dean and his team. Met armorers crafted a battle harness with complete torso protection, front and back, for about 8.5 pounds With pauldrons (shoulder guards), couters (elbow) and vambraces (forearm), add another 4 pounds With helmet -- and Dean offered the two finest battle helmets of modern times -- it all came to just over 15 pounds Quite wearable, you would think, given that U.S. soldiers' full panoply today can reach 40pounds, close to 15th century full-body plate armor.
Moreover, Dean's panoply was fully cushioned with "vulcanized sponge-rubber," and with the latest alloys, could stop a .45 ACP at 1000 ft. per second (and a rifle ball at 1250 ft. per second). In terms of coverage, ease and comfort, and raw protection, this was as close as anyone in the war came to the Holy Grail of personal body armor. Deployed in the big American Expeditionary Force (AEF) offensive at the Meuse-Argonne, it could have cut 26,000 battle deaths by one third or more.
So for arguments sake, lets say this armor was ordered adopted by the US Congress with Wilson signing off and crammed down the US Military establishment's throats with objectors sacked and thrown out the door, and enough sets are available for every Infantryman taking part in the Meuse-Argonne Offensive.
I would say AEF causalities would go down far more substantially than a third, because soldiers whose armor stops an incapacitating shell splinter and still has working limbs can continue providing suppressing fire and moving forward to grenade range. In fact, some the objectives not met in the first phase OTL might actually be taken, though its an open question on the 35th Division which had recently had its commanders relieved.
But the real changes come post war with soldiers and officers (many who would be Generals in WW2) seeing that this armor works and wanting to keep it and improve upon it while fighting off ignorant arguments that it can't stop rifle rounds which while true is not the main killer on the battlefield.
What do you guys think.