 Complete the following phrase:  He was imprisoned in the refugee camps at Gurs and Argelès-sur-Mer in southern France until fleeing to the Soviet Union, where he resumed his studies at Járkov Ukraine, until the invasion of the Soviet Union in 1941. He tried to join the Red Air Force but the Soviet commanders declined to take Spanish pilots, so he had to join a unit of miners and nighttime saboteurs operating in the Azov area. In 1942, he was accepted into the VVS along with several other former Republican pilots and participated in the defense of the Baku area during the Battle of the Caucuses. In 1943, he led the aerial escort for Stalin in his trip to Tehran for the 