The United States has had a triad of strategic nuclear weapons—land-based intercontinental ballistic missiles (ICBMs), submarine-launched ballistic missiles (SLBMs) on ballistic missile submarines (SSBNs), and long-range bombers—since the early 1960s. These systems have been the subject of many arms-control treaties between the United States and the Soviet Union/Russia. In their current configuration, US strategic nuclear weapons serve primarily to deter Russia and China from initiating major nuclear wars against the United States and its allies.
Additionally, at one time, the United States and the Soviet Union each had many thousands of nonstrategic nuclear weapons (NSNWs)—of many types—that were not covered by any treaties until the Intermediate Nuclear Forces (INF) Treaty banned several types of US and Soviet weapons in 1987. These US weapons were intended to provide a fallback option against extremely powerful conventional aggression and to deter enemy use of nuclear weapons in a previously conventional war. The number and variety of US NSNWs has declined by more than 90 percent since the 1980s because of the INF Treaty and various unilateral decisions (such as the Presidential Nuclear Initiatives, or PNI, of 1991). By contrast, Russia still has a large force of NSNWs and is modernizing these weapons.
In addition to the imbalance in NSNW arsenal size, there are significant performance deficiencies in US NSNWs, which are limited to unguided bombs carried by non-stealthy short-range fighters at bases in NATO countries. In particular, the bases are vulnerable to preemptive attacks (large conventional attacks, small nuclear attacks, or both). Moreover, the aircraft have questionable survivability against modern air defenses and provide limited geographic coverage without aerial refueling, which is infeasible in contested airspace. Finally, unguided bombs have an uncertain ability to achieve high lethality against hard targets without causing major collateral damage.
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