Following Germany's invasion of the Soviet Union in June 1941, Britain and the Soviet Union became allies. Both saw the newly opened Trans-Iranian Railroad as a strategic route to transport supplies from the Persian Gulf to the Soviet Union and were concerned that Reza Shah was sympathetic to the Axis powers, despite his declaration of neutrality. In August 1941, Britain and the Soviet Union invaded Iran and deposed him in favor of his son Mohammad Reza Pahlavi. Following the end of the Second World War, both countries withdrew their military forces from Iran.