Routine photo reconnaissance flights over Cuba revealed that the Soviet Union was, in fact, in the process of placing nuclear-armed missiles on that island. In response, the United States let it be known that any use of those missiles against any country in the Western Hemisphere would be considered as an attack on the United States and a full nuclear response on the Soviet Union would be the result. The United States and the Soviet Union stood eyeball to eyeball at the brink of a nuclear exchange.