An Intercontinental Ballistic Missile - ICBM for short - is a rocket built to deliver weapons across continents. It flies up into space, coasts in a long arc, and drops back down toward its target. The first ICBMs were developed in the late 1950s by the United States and the Soviet Union during the Cold War. They could cross between continents in about 30 minutes.
At the top of their flight path, ICBMs reach speeds above 15,000 mph - faster than almost anything humans build that isn’t going into orbit. They climb to over 700 miles in altitude before falling back down. Defending against one is incredibly hard precisely because they move so fast and come from so high up.
The technology that built ICBMs also opened up space exploration. Many famous launch vehicles are direct descendants of missile designs. The Atlas rocket that launched the first American to orbit started as an ICBM. So did Russia’s R-7, the ancestor of today’s Soyuz. The same engineering that made Cold War weapons also carried humans to the moon.
