By the end of 1941, Adolf Hitler had every reason to believe he would win the war in Europe and the Third Reich would rule for a thousand years. His invasion of the Soviet Union had that country on the verge of defeat. The U.S. and Great Britain — itself under siege — were desperate to save their unlikely ally and its leader Soviet Dictator Josef Stalin. To do so, President Roosevelt sent emissaries to Moscow to offer him wartime aid through the "Lend Lease" program.

"Once Stalin understands what's happening to his Red Army and Soviet state, there is a realization on his part that he must have allies wherever he can achieve it," explained Col. David Glantz, an historian retired from the U.S. Army. "Therefore he welcomes Roosevelt's emissaries. He welcomes the offers for Lend Lease."

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The Lend Lease program provided material aid to America's Allies and aid soon began to flow to the Eastern Front. In addition to air and sea routes to Siberia and Russia's far north, one of the key routes was through Iran, situated on the Soviet Union's southern border.

Iran, however, was not always a friend of the Allied powers. When World War II began, the country, under the leadership of its king, Reza Shah, had strong German sympathies. The British and Soviets understood this danger and in September 1941 took control of the country. They deposed the reigning Shah and established his 21-year-old son, Mohammed Reza Pahlavi, on the throne (Reza Pahlavi would reign for almost 50 years until deposed in the 1979 revolution.) The young Shah signed an agreement to work with the Allies and provide logistical support in moving Lend Lease aid to the Soviet Union.

"The first shipments come in the fall, September, October, 1942," said Glantz. "They don't begin in large numbers until November and December on the great land route through Tehran."

Known as the "Persian Corridor," U.S. ships sailed into the Persian Gulf and docked at various ports on Iran's southern coast. From there, the material –- including armaments, trucks and Studebakers — was loaded onto train transports heading north. Thousands of Iranian civilians played a role in the war effort from laborers for road building and driving to skilled mechanics at the truck assembly plants. The highways and Iranian State Railway became a vital life line for goods produced in American factories to the Soviet frontlines.

In 1943, Tehran was chosen as the site of the first of two meetings between the big three -– Churchill, Roosevelt and Stalin. Zoya Zarubina worked for the Soviet Delegation as one of Stalin's translators at the Tehran Conference. She remembers the high drama surrounding the visit: "The city was filled with German spies and all that, and there were rumors that they might be getting some ideas about a conspiracy."

"First of all there was a complete black out," said Zarubina. "So the people in Iran were very frightened because for three days there was nothing, no news."

For four days the British, American and Soviet leaders met secretively at the Soviet Embassy in Tehran. "It was an old aristocratic mansion and I was translating the war bulletins from Russian into English," said Zarubina.

The decisions made at the Tehran conference affected the outcome of the war and the post-war landscape for decades, including the opening of a second front into Western Europe in 1944 and the establishment of an organization of United Nations after the war.

In all, the "Persian Corridor" was the route for 4,159,117 tons of cargo delivered to the Soviet Union during the War. After Germany was defeated, Iran under the Shah remained an ally of the U.S. and Great Britain for decades, until he was overthrown in the Islamic Revolution in 1979 and replaced as Iranian leader by Ayatollah Khomeini.

— Gregory Johnson is a producer for "War Stories"