who made the nuclear bomb

The nuclear bomb was developed primarily through the Manhattan Project, a secret research and development program during World War II led by the United States with collaboration from the United Kingdom and Canada. The project was directed by Major General Leslie Groves, while J. Robert Oppenheimer, an American theoretical physicist, served as the director of the Los Alamos Laboratory where the bomb's design and development took place. Oppenheimer is often called the "father of the atomic bomb" for his central role in overseeing the research and design of the first nuclear weapons. The Manhattan Project involved prominent scientists such as Leo Szilard, who helped initiate the project with a letter to President Roosevelt warning about nuclear weapons, and Hans Bethe, who contributed key theoretical physics to make the bomb possible. The efforts resulted in two types of atomic bombs: the uranium- based "Little Boy" and the plutonium-based "Fat Man," both of which were used in 1945. The initial theoretical possibility of the bomb stemmed from the discovery of nuclear fission in 1938 by Otto Hahn and Fritz Strassmann, explained theoretically by Lise Meitner and Otto Frisch, which made an atomic bomb possible in theory. The development and construction were an enormous industrial and scientific enterprise costing about $2 billion (equivalent to about $27 billion today) and involving around 130,000 people at its height.