The Anglo-Soviet Invasion of Iran also known as Anglo-Soviet Invasion of Persia was the invasion of the Empire of Iran during World War II by Soviet, British and other Commonwealth armed forces. The invasion lasted from 25 August to 17 September 1941, and was codenamed Operation Countenance. The purpose was to secure Iranian oil fields and ensure Allied supply lines for the Soviets, fighting against Axis forces on the Eastern Front. Though Iran was officially neutral, according to the Allies its monarch Rezā Shāh was friendly toward the Axis powers and was deposed during the subsequent occupation and replaced with his young son Mohammad Reza Pahlavi.