An Intercontinental Ballistic Missile (ICBM) is a land-based, rocket-propelled, guided ballistic missile designed to deliver warheads over distances exceeding 5,500 kilometers. This weapon system was developed during the Cold War to solve the problem of delivering nuclear warheads to distant targets, establishing a capability for long-range strategic strikes. The concept grew out of Nazi Germany's V-2 rocket program. The Soviet Union's R-7 Semyorka was the first ICBM, with a successful full-range flight on August 21, 1957, and an improved variant, the R-7A, became operational in early 1960.
An ICBM's flight follows a high, arcing, ballistic trajectory with three phases. The initial boost phase is the powered portion, lasting about 2 to 5 minutes, where the missile uses multiple rocket stages to reach space. The missile is guided only during this brief phase. The longest phase is the unpowered midcourse phase, where the missile travels outside the atmosphere, following a trajectory determined by gravity and its initial velocity. Finally, the warhead enters the terminal reentry phase, plummeting toward the target at high speed. Modern ICBMs often employ Multiple Independently Targetable Reentry Vehicles (MIRVs), allowing a single missile to strike several separate targets.
ICBMs are central to the concept of strategic stability and are regulated by international arms control agreements. The Anti-Ballistic Missile (ABM) Treaty, signed in 1972 by the US and the Soviet Union, limited defensive systems against ICBMs to preserve the deterrent effect of offensive forces. The US unilaterally withdrew from the ABM Treaty in June 2002, leading to its termination. The New START Treaty, which entered into force in February 2011 between the US and Russia, replaced the earlier START I. It limits both sides to 1,550 deployed nuclear warheads and 700 deployed delivery systems. The treaty was extended until February 2026, but Russia suspended its participation in February 2023. New ICBMs, such as Russia's RS-28 Sarmat, are being developed with advanced capabilities to bypass existing missile defense systems.