 Complete the following phrase:  During World War II, he was active in the Soviet Union, premiering new concerti by Nikolai Miaskovsky and Aram Khachaturian as well as two sonatas by his friend Sergei Prokofiev. He was also awarded the Stalin Prize in 1942. The final years of the war saw the blossoming of a friendship with Shostakovich, which would lead to the two violin concertos and the sonata, all of which were to be premiered by and become firmly associated with Oistrakh in the following years. Oistrakhs career was set from this point, although the Soviet Union was protective of its people and refused to let him perform abroad. He continued to teach in the Moscow Conservatory, but when 