A penetration aid is a device or tactic used to increase an intercontinental ballistic missile (ICBM) warhead's chances of penetrating a target's defenses. An intercontinental ballistic missile (ICBM) is a ballistic missile with a long range (greater than 5,500 km or 3,500 miles) typically designed for nuclear weapons delivery (delivering one or more nuclear warheads). Due to their great range and firepower, in an all-out nuclear war, land-based and submarine-based ballistic missiles would carry most of the destructive force, with nuclear-armed bombers having the remainder.