Tsar Bomba C), north of the Arctic Circle over the Novaya Zemlya archipelago in the Arctic Ocean. The bomb was dropped from an altitude of ; it was designed to detonate at a height of over the land surface ( above sea level) by barometric sensors. The original, November 1961, United States Atomic Energy Commission estimate of the yield was 55–60 megatons, but since 1992, all Russian sources have stated its yield as 58.6 megatons. First secretary Khrushchev warned in a filmed speech to the Supreme Soviet of the existence of a 100-megaton bomb (technically the design was capable of this yield.)
Novaya Zemlya detected by German U-boats and visually confirmed by German reconnaissance aircraft. On the night of July 4, the German battleship "Tirpitz" and the heavy cruisers "Admiral Scheer", "Lutzow", and "Hipper," closed on PQ-17 and sank four allied merchant ships. The British Admiralty responded by diverting the convoy’s escort vessels to the west to engage the German warships, and ordered the now-vulnerable merchant vessels to scatter. Seeking the hoped-for sanctuary of Matochkin Strait, several of the ships headed toward Novaya Zemlya at flank speed. S.A. Kerslake, a crew-member aboard the British Trawler "Northern Gem", recorded in his diary: …we were making