American units fighting Tausūg guerrillas in the Moro Rebellion in Sulu during the Philippine–American War using the then-standard Colt M1892 revolver, .38 Long Colt, found it to be unsuitable for the rigors of jungle warfare, particularly in terms of stopping power, as the Moros had high battle morale and often used drugs to inhibit the sensation of pain. The U.S. Army briefly reverted to using the M1873 single-action revolver in .45 Colt caliber, which had been standard during the late 19th century; the heavier bullet was found to be more effective against charging tribesmen. The problems prompted the Chief of Ordnance, General William Crozier, to authorize further testing for a new service pistol.