According to a 2001 book by his former handler Alexander Feklisov, Rosenberg was originally recruited to spy for the interior ministry of the Soviet Union, NKVD, on Labor Day 1942 by former spymaster Semyon Semyonov. By this time, following the invasion by Nazi Germany in June 1941, the Soviet Union had become an ally of the western powers, which included the United States after Pearl Harbor. Rosenberg had been introduced to Semyonov by Bernard Schuster, a high-ranking member of the Communist Party USA and NKVD liaison for Earl Browder. After Semyonov was recalled to Moscow in 1944 his duties were taken over by Feklisov.