Intercontinental Ballistic Missile

An intercontinental ballistic missile (ICBM) is a ballistic missile with a range of more than 5,000 km (3,100 miles) typically designed for nuclear weapons delivery (delivering one or more nuclear warheads). Most modern designs support multiple independently targetable reentry vehicles (MIRVs), allowing a single missile to carry several warheads, each of which can strike a different target.

Early ICBMs had limited accuracy that allowed them to be used only against the largest targets such as cities. They were seen as a "safe" basing option, one that would keep the deterrent force close to home where it would be difficult to attack. Attacks against military targets, if desired, still demanded the use of a manned bomber. Second and third generation designs dramatically improved accuracy to the point where even the smallest point targets can be successfully attacked. Similar evolution in size has allowed similar missiles to be placed on submarines, where they are known as submarine launched ballistic missiles, or SLBMs. Submarines are an even safer basing option than land-based missiles, able to move about the ocean at will. This evolution in capability has pushed the manned bomber from the front-line deterrent force in all forces but the United States and Russia, and land-based ICBMs have similarly given way largely to SLBMs.

ICBMs are differentiated by having greater range and speed than other ballistic missiles: intermediate-range ballistic missiles (IRBMs), medium-range ballistic missiles (MRBMs), short-range ballistic missiles (SRBMs)—these shorter range ballistic missiles are known collectively as theatre ballistic missiles. There is no single, standardized definition of what ranges would be categorized as intercontinental, intermediate, medium, or short. Additionally, ICBMs are generally considered to be nuclear only; although several conceptual designs of conventionally armed missiles have been considered, the launch of such a weapon would be such a threat that it would demand a nuclear response, eliminating any military value of such a weapon.