Nuclear fission the Manhattan Project during World War II (September 1, 1939 – September 2, 1945) carried out most of the early scientific work on fission chain reactions, culminating in the three events involving fission bombs that occurred during the war. The first fission bomb, codenamed "The Gadget", was detonated during the Trinity Test in the desert of New Mexico on July 16, 1945. Two other fission bombs, codenamed "Little Boy" and "Fat Man", were used in combat against the Japanese cities of Hiroshima and Nagasaki in on August 6 and 9, 1945 respectively. Even the first fission bombs were thousands of
B41 nuclear bomb of 50 or 100 megatons of TNT, depending on its own configuration as a "clean" (lead encased) or dirty (uranium encased) bomb. However even at the Tsar Bomba's theoretical maximum yield of 100 megatons, it would still only achieve a yield to weight ratio of ~ 3.7 Megaton/tonne, thus the B-41 is the most efficient, highest yield to weight ratio, weapon ever created. However, since neither full yield versions of the B-41 nor "Tsar Bomba" were ever demonstrably tested, the B-41's high efficiency is merely theoretical; the most efficient tested and proven nuclear physics package is the W56. If detonated