TSAR, was a thermonuclear aerial bomb, and the most powerful nuclear weapon ever created and tested. The Soviet physicist Andrei Sakharov oversaw the project at Arzamas-16, while the main work of design was by Sakharov, Viktor Adamsky, Yuri Babayev, Yuri Smirnov [ru], and Yuri Trutnev. The project was ordered by Nikita Khrushchev in July 1961 as part of the Soviet resumption of nuclear testing after the Test Ban Moratorium, with the detonation timed to coincide with the 22nd Congress of the Communist Party of the Soviet Union
Tested on 30 October 1961, the test verified new design principles for high-yield thermonuclear charges, allowing, as its final report put it, the design of a nuclear device "of practically unlimited power".The bomb was dropped by parachute from a Tu-95V aircraft, and detonated autonomously 4,000 metres (13,000 ft) above the cape Sukhoy Nos of Severny Island, Novaya Zemlya, 15 km (9.3 mi) from Mityushikha Bay, north of the Matochkin Strait.The detonation was monitored by United States intelligence agencies, via a KC-135A aircraft (Operation SpeedLight) in the area at the time. A secret U.S. reconnaissance aircraft named "Speed Light Alpha" monitored the blast, coming close enough to have its antiradiation paint scorched.