The Petlyakov Pe-8, originally known as the TB-7, was a Soviet heavy bomber designed before World War II, the only four-engined bomber the USSR built during the war. Produced only in small numbers it bombed Berlin in August 1941 as well as other cities in Germany and Finland on so-called "morale raids" to raise the morale of the Soviet people by exposing German vulnerabilities. But its primary mission was to attack German airfields, rail yards and other rear-area facilities at night, although it flew the People's Commissar of Foreign Affairs (Foreign Minister) Vyacheslav Molotov from Moscow to the United States in 1942. Sources disagree if the Pe-8 was withdrawn from combat operations in 1944, but the surviving aircraft were withdrawn from service after the end of the war. Some aircraft were modified as VIP transports while others were used in various testing programs. Some were used in support of Soviet Arctic operations until the late 1950s.