ICBM

Intercontinental Ballistic Missiles (ICBMs) are the land-based leg of the nuclear triad, designed to deliver nuclear warheads across intercontinental distances. The United States deploys 400 Minuteman III ICBMs in hardened underground silos across Montana, Wyoming, North Dakota, Colorado, and Nebraska. Russia operates a mix of silo-based and road-mobile ICBMs, including the heavy SS-18 Satan and the newer RS-28 Sarmat.

An ICBM launch follows a three-phase trajectory: the boost phase, lasting about five minutes while the rocket motors burn; the midcourse phase, during which the warhead travels through space on a ballistic arc; and the terminal phase, when it reenters the atmosphere and descends toward its target at speeds exceeding Mach 20. Modern ICBMs carry multiple independently targetable reentry vehicles (MIRVs), allowing a single missile to strike several separate targets.

ICBMs are valued for their responsiveness, they can be launched within minutes of a presidential order, and their survivability in hardened silos. However, their fixed locations make them potentially vulnerable to a preemptive first strike, which is why the nuclear triad distributes deterrence across ICBMs, submarine-launched missiles, and strategic bombers to ensure that no single attack could eliminate America's ability to retaliate.