During the Cold War, the United States began developing ballistic missiles with nuclear warheads. At first, the range of these weapons was limited but after extensive research, it was increased to over thousands of miles. Long ranges of ballistic missiles give them the capability to be launched from one continent and target another. This fact gives these long-range nuclear weapons the name intercontinental ballistic missiles (ICBM). The evolution of these weapons, from liquid fuel and single warhead to solid fuel, more extensive range and multiple warheads, was of the highest importance to the arms race in the Cold War.