According to Mark M Boatner, The Biographical Dictionary of World War II, the USSR rank corresponding to US full general was introduced on 7 May 1940 but it was not until 4 June 1940 that the first recipients Meretskov, Tyulenov and Zhukov were listed in Pravda.
The US rank General of the Army (five-star insignia) corresponding to marshal of the Soviet Union was introduced on 14 December 1944 (Public Law 482, 78 Congress on 14 December 1944).