In May 1958, with the Soviet Union pulling ahead in the early space race, the United States Air Force quietly funded a classified study called Project A119. The project's task was to investigate the feasibility of detonating a nuclear weapon on the surface of the Moon as a public demonstration of American technological and military reach.

The study was led at the Armour Research Foundation in Chicago by the physicist Leonard Reiffel. The plan called for a relatively small nuclear device — a W25 warhead, with a yield of roughly 1.7 kilotons, about a tenth of the bomb dropped on Hiroshima. The weapon would be carried by an intercontinental ballistic missile and detonated near the lunar terminator, the line dividing the lit and unlit halves of the Moon. A flash on the dark side would be clearly visible from Earth with the naked eye, and would broadcast American capability to the world without ambiguity.

The team included physicists, astronomers, and at least one young researcher named Carl Sagan, who was tasked with calculating the behavior of the dust cloud the explosion would produce in the Moon's vacuum and low gravity.

The project was cancelled in 1959. The reasons given combined fallout risk, the scientific community's objection that the lunar surface — untouched for several billion years — would be irreversibly altered, and a public-relations concern that the United States would be perceived as a destroyer of a shared cosmic neighbor rather than a peaceful explorer.

The existence of Project A119 remained classified for four decades. Reiffel disclosed it publicly in 2000, after declassification. Documents released in subsequent years confirmed his account in detail. The Soviet Union, it turned out, had developed a parallel concept of its own — Project E-4 — also abandoned for similar reasons.

Both superpowers had seriously considered, then rejected, lighting up the Moon to win an argument.