Anglo-Soviet invasion of Iran

The Anglo-Soviet invasion of Iran, also known as the Anglo-Soviet invasion of Persia or the Allied invasion of Iran, was the joint invasion of the officially neutral Imperial State of Iran by the United Kingdom and the Soviet Union in August 1941. The two powers announced that they would stay until six months after the end of the war with their mutual enemy, Nazi Germany (World War II), which turned out to be 2 March 1946. On that date the British began to withdraw, while the Soviet Union delayed until May, initially citing "threats to Soviet security", followed by the Iran crisis of 1946.

The invasion, code named Operation Countenance, was largely unopposed by the numerically and technologically outmatched Iranian forces. The multi-pronged coordinated invasion took place along Iran's borders with the Kingdom of Iraq, Azerbaijan SSR, and Turkmen SSR, with fighting beginning on 25 August and ending on 31 August when the Iranian government, under the rule of Reza Shah Pahlavi, formally agreed to surrender, having already agreed to a ceasefire on 30 August.

The invasion took place two months after the Axis invasion of the Soviet Union and the Soviet Union's subsequent alliance with the United Kingdom. The attack also took place less than two months after Allied victories over pro-Axis forces in neighboring Iraq, French Syria and Lebanon. The invasion's strategic purpose was to ensure the safety of Allied supply lines to the USSR (see the Persian Corridor), secure Iranian oil fields, limit German influence in Iran (due to the presence of Germans in Iran, mainly for industrial purpose) and preempt a possible Axis advance from Turkey through Iran toward the Baku oil fields or British India. Following the invasion, on 16 September 1941 Reza Shah was forced to abdicate and went into exile, being replaced by his young son Mohammad Reza Pahlavi. Iran would remain under British and Soviet occupation until 1946.