The Cuban Missile Crisis was perhaps the closest the world has ever come to all-out nuclear war, and it all started with a photo.

On October 15, 1962, Dino Brugioni, a senior analyst at the US’s newly formed National Photographic Interpretation Center, identified missile trailers measuring approximately 65 feet in length in an aerial reconnaissance photo. Those trailers were a match for the Soviet SS-4, a medium-range ballistic missile that could reach a huge amount of the United States, including Washington, DC.

Upon seeing this photo, US President John F. Kennedy ordered more aerial recon flights, conducted by the CIA using a high-altitude U-2 spy plane. Kennedy used these photographs to make a plan of action about confronting the Soviet Union over their secretive installation of offensive missiles in Cuba.

To learn more about photography’s role in the crisis, check out the video above. And for more Vox videos, make sure to subscribe to our YouTube channel.