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Since Russia has traditionally been a British rival in Asia, what if it achieved its ambition of a port in the Persian Gulf by invading Iran in late 1939? This would also give it access to the Abadan oilfields, probably more important than securing Karelia from Finland.
The British and French had made some plans for this, including the bombing of the Baku oilfields, and the sending of troops from India, but didn't want to risk war with the USSR while also fighting Germany. What might have been the consequences, and the reaction of UK, France, Germany?
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