During the Cold War, both sides pursued a policy know as MAD—Mutually Assured Destruction. Each knew, especially when ICBMs were introduced, if one attacked, the other would be obliterated in 30 minutes.
Both side's ICBMs began as liquid fueled rockets. For the U.S., it was the Atlas and the Titan series. But having to fuel the rockets delayed the ability to launch quickly. As soon as solid propellant technology developed sufficiently, the U.S. went with it. The first was the Minuteman. It could be launched on a moment’s notice.
Today, we have Minuteman III, a larger, more powerful rocket that carries multiple warheads.
But there is another solid propellant rocket in the arsenal. Somewhere, in the oceans of the world, are 18 stealthy submarines carrying 24 Trident missiles. No potential enemy knows where these subs are. Each Trident carries multiple warheads. The rocket has a range of at least 4000 miles. It most likely is 5000.
Trident is the third generation of the first solid propellant strategic missile, the Polaris, and the Poseidon, also sub launched.In the illustration, the first three missiles on the left are Polaris', the middle two are Poseidons and the one on the right is the Trident.