Wikipedia

Project A119, also known as A Study of Lunar Research Flights, was a top-secret plan developed in 1958 by the United States Air Force. The aim of the project was to detonate a nuclear bomb on the Moon, which would help in answering some of the mysteries in planetary astronomy and astrogeology. If the explosive device detonated on the surface, and not in a lunar crater, the flash of explosive light would have been faintly visible to people on Earth with their naked eye. This was meant as a show of force resulting in a possible boosting of domestic morale in the capabilities of the United States, a boost that was needed after the Soviet Union took an early lead in the Space Race.