Why did they make the nuclear bomb?

Answer 1

The US, working with the British, developed the atomic bomb, as it was then called, because it was believed that Nazi Germany was well on the way to making one and it was necessary to be able to match them if they began to use, or threatened to use, such a weapon. As it turned out, the Germans had not been able to overcome technical as well as political problems and were never near to construction of an atomic bomb. Germany surrendered before the American/British effort had been completed. The bomb, once developed, was used on Japan to bring the Pacific war to a sudden end. While there has been subsequent controversy about whether the bomb should have been used on Japan, at the time there were very few people who were aware of the bomb's existence and capabilities and who thought it ought not to be used. Most of those few thought that a demonstration on an unpopulated location should be made first.