The Cold War was an unusual period for both the United States and the Soviet Union. Both sides were desperate to have the upper hand and ensure that if either side attacked, they would be able to retaliate or beat them to the punch. To that end, there were a number of different Cold War plots and ideas that served a variety of purposes.
Some were meant to be a warning, showing the other side what they were capable of, some were to get information, and others were to figure out alternative uses for the massive number of nuclear weapons that both sides possessed. Some of the plots and schemes were successful, brilliant, and advanced the military strategy and capabilities of their respective countries…others, not so much.
Project A119 was one of the more potentially devastating plots of the Cold War era. In 1958, the plan was developed by the United States Air Force under the pretense of learning more about astronomy and astrogeology. The truth of the matter was that it was really supposed to be a bit of a PR mission. The plan was to detonate a nuclear bomb on the surface of the moon.
There were a few justifications for why this was a good idea (and a few thousand reasons why it was a bad one). The first reason was that if they were able to detonate a nuclear bomb on the surface of the moon (as opposed to in a crater), the flash of the explosion would be seen from Earth by the naked eye. This would be a significant display of American capabilities that would hopefully get the world to forget that the Soviets were able to launch the first satellite into space, and that the latest attempts of the United States to launch their own satellite had ended in disaster.
Another reason why the Air Force was interested in such an idea was the rumor that the Soviet Union was planning to detonate a hydrogen bomb on the surface of the moon in celebration of the October Revolution. The Air Force had contemplated a hydrogen bomb as well, but there were concerns about it being too heavy. Research into the project raised a number of concerns, not the least of which was the fact that if the bomb failed to hit the moon it had a high probability of returning to Earth.
Ultimately the project was scrapped because there were concerns that the public would react negatively to the detonation and it would not be the morale booster that the Air Force was looking for. There was also the concern of danger to the public and the unknowns involved with lunar nuclear fallout and its impact on potential lunar colonization.