Again I go back to the Philippine-American ( Philippine Insurrection) war where the 45's were getting the job done and the 38's were not
Uhhhh ... no.
It's important to note a few historical facts before everyone gets twisted up around half-truths and war stories.
The "38" in question was NOT a .38spl, as used in most modern revolvers. It was the ".38 Long Colt". The specific round in question was likely a 150-grain, 9.2mm projectile, traveling at a muzzle-velocity of ~750fps, producing no more than about 200 ft/lbs of force.
They did not (in the Philippine Insurrection) switch to a pistol firing the modern .45ACP round. They switched
back to ".45 Long Colt" fired from a six-shot, single-action revolver.
The switch back to .45 Long Colt did not produce better results. It was not a problem of ballistics, but rather one of poor shot placement and very determined adversaries, using a primitive form of body armor.
Nonetheless, military officials (not knowing what we know today about terminal ballistics) were convinced that a "bigger bullet" was the solution to the problem. This was also reinforced by the fact that the best-known 9mm pistols of the time were notoriously unreliable, and the 9mm rounds commonly available at the time were pathetic, compared to what is available today.
This is what led to the development of the modern .45ACP round as well as the 1911 pistol design.
It's interesting to note that the .45ACP round is
smaller in diameter than .45LC, travels at a slower velocity, and produces less energy. If the .45LC did not "solve the problem", the .45ACP would not have done so either.