The Allies worried that Germany would look to neutral Iran for oil. Soon the Allies questioned themselves about Iranian neutrality and they gave Reza Shah a final warning to remove the German workers. He refused once again. In August 1941, the British and Soviet troops invaded Iran (Operation Countenance) and, in September 1941, forced Reza Shah Pahlavi to abdicate his throne. He was replaced by his son Mohammad Reza Shah Pahlavi, who was willing to enter the war on the side of the Allies. Iran became known as "The Bridge of Victory".