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. Its purpose was to secure Iranian oil fields and ensure Allied supply lines (see Persian Corridor) for the USSR, fighting against Axis forces on the Eastern Front. Though Iran was neutral, the Allies considered King Reza Shah to be friendly to the Axis powers, deposed him during the subsequent occupation and replaced him with his young son Mohammad Reza Pahlavi.