“Ever since the 1840s the standard Army sidearm had been the .45-caliber single-action pistol. This old horse gun was a big, ugly thing that required an outsized trigger guard to accommodate the gloved finger of a cavalryman, but it had been a supremely effective weapon in conquering the American Indian. In 1892 the Army replaced it with a smaller .38 revolver, which was lighter, easier to fire, and more accurate. The fact that it had less stopping power was considered to be “no material disadvantage,” although the Army covered itself in a test report by admitting, “The question can only be definitely settled by actual trial against living objects.” The .38 failed that essential test in the Philippines, and line officers pleaded for a modern sidearm with the power of the old .45 pistol.”
The Islamic Moro Pirates in the Philippines would wrap wide leather bands around their major muscles and abdomen, which would shrink when moistened with sweat, then smoke hashish. A .38 would pass through them with minimal damage, but a .45 would leave a large, gaping wound on both sides, usually incapacitating an attacker, who typically would have charged a US position with a Bolo knife or sword, intent on mutilating the officer shooting at them.