In the midst of World War II, in June 1941, Nazi Germany broke the Molotov–Ribbentrop Pact and invaded the Soviet Union, Iran's northern neighbor. The Soviets quickly allied themselves with the Allied countries and in July and August, 1941 the British demanded that the Iranian government expel all Germans from Iran. Reza Shah refused to expel the Germans and on 25 August 1941, the British and Soviets launched a surprise invasion and Reza Shah's government quickly surrendered. The invasion's strategic purpose was to secure a supply line to the USSR (later named the Persian Corridor), secure the oil fields and Abadan Refinery (of the UK-owned Anglo-Iranian Oil Company), prevent a German advance via Turkey or the USSR on Baku's oil fields, and limit German influence in Iran. Following the invasion, on 16 September 1941 Reza Shah abdicated and was replaced by Mohammad Reza Pahlavi, his 21-year-old son.