Question: why was 45 acp developed?
Answer: The .45 ACP (Automatic Colt Pistol) or .45 Auto (11.43×23mm) is a handgun cartridge designed by John Moses Browning in 1904, for use in his prototype Colt semi-automatic pistol. ... The round was developed due to a lack of stopping power experienced in the Moro Rebellion using the .38 Long Colt.