The phrase, “The Great Game” usually describes the Anglo-Russian rivalry that played out across Central Asia, especially Afghanistan, in the 19th century, but has its roots in an earlier (and eventually overshadowed) rivalry between the two Great Powers in Persia, modern Iran. For hundreds of years, the Iranian people and shahs were used for both good and ill in the diplomatic, economic, and military maneuvering of the British and Russian Empires. In the late 19th century, Iran began asserting its own political independence by establishing ties to the new German Empire. In 1925, a new Shah came to power, Reza Shah Pahlavi, and began a massive modernization program funded by the nationalization of the Anglo-Iran Oil Company (Today we know them as BP), and much foreign assistance, particularly German and Italian.
Reza Shah declared neutrality at the outset of the Second World War, but both Great Britain and the Soviet Union suspected that German advisors in the economy and to the Shah had outsized influence over Iranian foreign policy. After the German Invasion of the Soviet Union in June 1941, Stalin was desperate for Lend Lease supplies and FDR was more than willing to provide them, but the convoy routes through the Arctic Circle were especially dangerous. The old Anglo-Russian trade routes through Iran, especially the railroad from the Persian Gulf to the Caspian Sea known as the “Persian Corridor”, were a perfect compliment.
By the summer of 1941, the Red Sea, Gulf of Aden, Arabian Sea, and northern Indian Ocean were no longer considered war zones, and could be freely transited by American ships. The British had just secured Ethiopia, Somaliland, and Eritrea from the Italians, cleared Iraq of Fascists, and threw out the Vichy French from Syria, which released several Indian divisions for duty elsewhere. The Soviets additionally wanted an excuse to seize Iran as the next Socialist republic, and secure the oil fields around the Caspian Sea. Britain also saw a pro German Iran as a destabilizing influence to eastern India, and neutral Turkey. When British diplomats delivered an ultimatum to the Shah on 17 August 1941 to expel all Germans from Iran, it didn’t matter what he said: Iran was going to be invaded.
On 24 August, British and Indian troops crossed into Iran from Diyala and Basra in Iraq, in a surprise attack which quickly defeated the Iranian Army that Shah Reza spent a decade and half modernizing with great difficulty. And his new roads expedited the invaders movement in the country. The next day, three Soviet armies did the same from the Transcaucasus and Turkmenistan. In just four days, Soviet and British troops met at Qazvin, just north east of Tehran, and the Shah sued for peace.
The first Americans to facilitate the Persian Corridor arrived a few days later (In 1941, British and Soviet troops were needed for fighting. By 1943, 30,000 Americans were serving in Iran maintaining the Persian Corridor). The first convoys and train loads of American supplies to the Soviet Union would commence in just a week. 30% of all Lend Lease supplies to the Soviet Union would transit through Iran.