This Persia was attacked by troops of the Third Reich on May 1st in 1942, the very same day when the Germans also invaded the Soviet Union, aiming for the oilfields in SW Persia and Azerbaijan. British troops (from India) and Russians (from Turkestan) marched into Persia to help defending it against Germany. After being replaced by the Americans, British troops (including many Indians) have been redeployed to the Persian front in 1943. The mountainous terrain makes the reconquest difficult, though, despite the fact that the Brits have gained numerical advantage against Generalfeldmarschall Rommel. Persia got the occupied areas back when Rommel capitulated in November 1944.