The Soviet Union entered World War II with the German invasion in 1941. From 1941 to 1943, Botvinnik gave all of his time to his work as an engineer, visiting and testing power stations, as well as repairing insulations. By the beginning of 1943, he was able to take up chess again on a limited basis, studying and playing two days per week. He won the strong Sverdlovsk 1943 tournament, and played hors concours in the 1943 Moscow Championship, winning with 13.5/16.