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
B61 nuclear bomb three flight tests of the B61-12 tail kit assembly. , the Pentagon was asking for an $11 billion life-extension program for the B61 bomb, which would be the most ambitious and expensive nuclear warhead refurbishment in history. Congress is opposed to this effort for cost and timeline issues and questions for the B61's need. Cost estimates have doubled from $4 billion to $8 billion and production slipped from 2017 to 2020, then grew to $10 billion for life extension plus $1 billion for tail guidance kits and production was delayed to 2021. Sequestration budget cuts in early 2013 have delayed