The Thompson–LaGarde Tests were a series of tests conducted in 1904 to determine which caliber should be used in American military handguns.
The Army had previously been using the .38 Long Colt, and the cartridge's relatively poor ballistics were highlighted during the Philippine–American War of 1899–1902, when reports from U.S. Army officers were received regarding the .38 bullet's inability to stop charges of frenzied Moro juramentados in the Moro Rebellion, even at extremely close ranges. A typical instance occurred in 1905 and was later recounted by Col. Louis A. LaGarde:
Antonio Caspi, a prisoner on the island of Samar, P.I. attempted escape on Oct. 26, 1905. He was shot four times at close range in a hand-to-hand encounter by a .38 Colt's revolver loaded with U.S. Army regulation ammunition. He was finally stunned by a blow on the forehead from the butt end of a Springfield carbine.
Col. LaGarde noted Caspi's wounds were fairly well-placed: three bullets entered the chest, perforating the lungs. One passed through the body, one lodged near the back and the other lodged in subcutaneous tissue. The fourth round went though the right hand and exited through the forearm. So the Army began looking for a solution. The task was assigned to Colonel John T. Thompson of the Infantry, and Major Louis Anatole LaGarde of the Medical Corps.
The tests were conducted at the Nelson Morris Company in Chicago, Illinois, using both live cattle outside a local slaughterhouse, as well as some human cadavers. To consider different combinations of factors, several different calibers were used during the tests: 7.65×21mm Parabellum (.30 Luger), 9×19mm Parabellum (Germany), .38 Long Colt, .38 ACP, blunt and hollow-point .45 Colt (US), .476 Eley (UK), and the "cupped" .455 Webley (UK).