First strike (nuclear strategy)

First-strike attack, the use of a nuclear first strike capability, was greatly feared during the Cold War between NATO and the Soviet Bloc. At various points, fear of a first strike attack existed on both sides. Misunderstood changes in posture and well understood changes in technology used by either side often led to speculation regarding the enemy's intentions.

• CEP – circular error probable; the radius within which a weapon aimed at a given point will land with a 50% confidence; for example, a CEP of 150 m indicates that 50% of the time, the weapon will impact within 150 m of the target. This measure of accuracy assumes that everything up to the point of impact works correctly.
• Range – the maximum distance from a target a weapon can be fired to successfully hit the point where it is targeted at. (When range is used without qualifiers, like maximum or minimum, it is assumed that it refers to maximum; however, many of these described weapons have minimum ranges as well, though they are not mentioned, or, in all likelihood, even known to the public.)
• kt/Mt – This is an approximate measure of how much energy is released by the detonation of a nuclear weapon; kt stands for kilotons TNT, Mt stands for megatons TNT. Conventional science of the period contemporary to the Manhattan project came up with these measures so as to reasonably analogize the incredible energy of a nuclear detonation in a form that would be understandable to the military, politicians, or civilians. Trinitrotoluene (TNT) was and is a high explosive with industrial and military uses, and is around 40% more powerfully explosive than an equivalent weight of gunpowder. A ton is equivalent to 1000 kg or approximately 2200 pounds. A 20 kt nuclear device, therefore, liberates as much energy as does the explosion of 20,000 tons of TNT (this is the origin of the term, for the exact definition see TNT equivalent). This is a large quantity of energy. In addition, unlike TNT, the detonation of a nuclear device also emits ionizing radiation that can harm living organisms, including humans; the prompt radiation from the blast itself and the fallout can persist for a long period of time, though within hours to weeks, the radiation from a single nuclear detonation will drop enough to permit humans to remain at the site of the blast indefinitely without incurring acute fatal exposure to radiation.

Because of the low accuracy (large circular error probable) of early generation intercontinental ballistic missiles (and especially submarine-launched ballistic missiles), counterforce strikes were initially only possible against very large, undefended targets like bomber airfields and naval bases. Later generation missiles with much improved accuracy made counterforce attacks against the opponent's hardened military facilities (like missile silos and command and control centers) possible. This is due to the inverse-square law, which predicts that the amount of energy dispersed from a single point release of energy (such as a thermonuclear blast) dissipates by the inverse of the square of distance from the single point of release. The result is that the power of a nuclear explosion to rupture hardened structures is greatly decreased by the distance from the impact point of the nuclear weapon. So a near-direct hit is generally necessary, as only diminishing returns are gained by increasing bomb power.

• Pershing II MRBM. Single warhead, variable yield 5-50 kt, CEP 50 m with active radar terminal guidance. Short, 7-minute flight-time and range of 1,800 km, designed to strike C⁴ISTAR installations, bunkers, air fields, air defense sites, and ICBM silos in the European part of the Soviet Union. Decommissioned.
• R-36 (NATO designation SS-18 "Satan"), MIRV. Believed to be a first-strike weapon by some in the West, due to high accuracy of 220 m CEP, and high throw-weight of 8,800 kg; could deploy 40 penetration aids and deliver at least 10 warheads of at least 500 kt through independent, separate targets. Each warhead could probably take out even hardened nuclear silos, such as those used by the Minuteman III. Deployed in 1976, aimed at CONUS. Still in service.
• LGM-118 Peacekeeper. Similar in capability to the SS-18 Satan, the Peacekeeper had a throw-weight of 4,000 kg, and could carry only 10 MIRVed warheads of 300 kt each, as well as a CEP of 120 meters. Deployed in the mid-1980s. Decommissioned; however, guidance systems and re-entry vehicles moved to Minuteman III missiles.
• SS-20 Saber MIRV IRBM. Deployed by the Soviet Union in the late 1970s, this MIRVed IRBM could hide out behind the Urals in Asian Russia and strike NATO C⁴ISTAR facilities in Europe with scarcely any warning, due to very short flight time, high accuracy, and MIRV payload (rare on an intermediate-range missile). Decommissioned.

• Any missile defense system capable of wide-area (e.g., continental) coverage, and especially those enabling destruction of missiles in the boost phase, is a first-strike-enabling weapon because it allows for a nuclear strike to be launched with reduced fear of mutual assured destruction. Such a system has never been deployed, although a limited continental missile defense capability has been deployed by the U.S., but it is capable of defending against only a handful of missiles.
  • This does not apply, in general, to terminal missile defense systems, such as the former U.S. Safeguard Program or the Russian A-35/A-135 systems. Limited-area terminal missile defense systems, defending such targets as ICBM fields, or C⁴ISTAR facilities may, in fact, be stabilizing, because they ensure survivable retaliatory capacity, and/or survivable de-escalation capacity.
  • This also might not apply to a "non-discriminatory" space-based missile defense system, even if it is—actually, precisely because it is—of global reach. Such a system would be designed to destroy all weapons launched by any nation in a ballistic trajectory, negating any nation's capability to launch any strike with ballistic missiles, assuming the system was sufficiently robust to repel attacks from all potential threats, and built to open standards openly agreed upon and adhered to. No such system has yet been seriously proposed.

Trident II D5 is one of the most advanced submarine-launched ballistic missiles

• UGM-133 Trident II missiles may carry up to 8, 100kt W76 (C4) or 12 (START-limited 8, SORT-limited 5) W76 or 475kt W88 MIRVed warheads (D5). The circular error probability of the weapons is classified but is believed to be less than 120 m (C4) and 100 m (D5). The missile attains a temporary low altitude orbit only a few minutes after launch. The guidance system for the missile is an inertial guidance system with an additional star-sighting system, which is used to correct small positional errors that have accrued during the flight. GPS has been used on some test flights but is assumed not to be available for a real mission. Trident I-C4 has a range of over 4,000 nmi, and the Trident II-D5 can surpass 6,000 nmi; however, the absolute ranges of the missiles are classified and withheld from public domain for reasons of national security.
• R-36 (SS-18 Satan) Mod I/II 25 megaton variant. Although it is widely accepted that Soviets never had a first-strike strategy because of their conventional arms superiority in Europe, some experts believed that the single-warhead 25 megaton version of R36-M (SS-18, CEP 250 m) was a first-strike weapon targeted against Minuteman III silos. However, a much more logical explanation comes from retired Soviet military officers, who report that the 25 megaton SS-18 was targeted against heavily fortified command-and-control facilities. The reason is that a single 25 megaton warhead could take out only one hardened missile silo if the silos are sufficiently separated—probably by only 2–4 km, depending on the amount of hardening because of the inverse square law, which predicts that the amount of energy dispersed from a single point release of energy (such as a thermonuclear blast) dissipates by the inverse of the square of distance from the single point of release. Therefore, the power of a nuclear explosion to rupture hardened structures is greatly decreased by the distance from the impact point of the nuclear weapon. Therefore, a nearly direct hit is generally necessary, as only diminishing returns are gained by increasing bomb power. The only purpose for gigantic nuclear weapons like the SS-18 25 megaton variant is to take out extremely hardened targets, like command-and-control facilities, such as NORAD, located at the Cheyenne Mountain Complex; Federal Emergency Management Agency (FEMA), located at Mount Weather; or Site R, located at Raven Rock. (The amount of energy needed to rupture missile silos is orders of magnitude greater than the amount necessary to destroy cities, which made the SS-18 25 megaton variant effective for the destruction of large urban centers, as well.) This could be a useful weapon for a decapitation strike, but that is a very risky move, and both the U.S. and Russia have extensive countermeasures against such methods.

According to the theories of nuclear deterrence and mutual assured destruction, full countervalue retaliation would be the likely fate for any state that unleashed a first strike. To maintain credible deterrence, nuclear-weapons states have taken measures to give their enemies reason to believe that a first strike would lead to unacceptable results.

The main strategy relies on creating doubt among enemy strategists regarding nuclear capacity, weapons characteristics, facility and infrastructure vulnerability, early warning systems, intelligence penetration, strategic plans, and political will. In terms of military capabilities, the aim is to create the impression of the maximum possible force and survivability, which leads the enemy to make increased estimates of the probability of a disabling counterstrike, and in terms of strategy and politics, the aim is to cause the enemy to believe that such a second strike would be forthcoming in the event of a nuclear attack.

A Minuteman III ICBM test launch from Vandenberg Space Force Base, United States

MIRVed land-based ICBMs are generally considered suitable for a first strike or a counterforce strike, due to:

1. Their high accuracy (small circular error probable), compared to submarine-launched ballistic missiles which used to be less accurate, and more prone to defects;
2. Their fast response time, compared to bombers which are considered too slow;
3. Their ability to carry multiple MIRV warheads at once, useful for destroying a whole missile field with one missile.

Unlike a decapitation strike or a countervalue strike, a counterforce strike might result in a potentially more constrained retaliation. Though the Minuteman III of the mid-1960s was MIRVed with 3 warheads, heavily MIRVed vehicles threatened to upset the balance; these included the SS-18 Satan which was deployed in 1976, and was considered to threaten Minuteman III silos, which led some neoconservatives ("Team B") to conclude a Soviet first strike was being prepared for. This led to the development of the aforementioned Pershing II, the Trident I and Trident II, as well as the MX missile, and the B-1 Lancer.

MIRVed land-based ICBMs are considered destabilizing because they tend to put a premium on striking first. When a missile is MIRVed, it is able to carry many warheads (up to 8 in existing U.S. missiles, limited by New START, though Trident II is capable of carrying up to 12[4]) and deliver them to separate targets. If it is assumed that each side has 100 missiles, with 5 warheads each, and further that each side has a 95 percent chance of neutralizing the opponent's missiles in their silos by firing 2 warheads at each silo, then the attacking side can reduce the enemy ICBM force from 100 missiles to about 5 by firing 40 missiles with 200 warheads, and keeping the rest of 60 missiles in reserve. As such, this type of weapon was intended to be banned under the START II agreement, however the START II agreement was never activated, and neither Russia nor the USA has adhered to the agreement.

Any defense system against nuclear missiles such as SDI will be more effective against limited numbers of missiles launched. At very small numbers of targets, each defensive asset will be able to take multiple shots at each warhead, and a high kill ratio could be achieved easily. As the number of targets increases, the defensive network becomes "saturated" as each asset must target and destroy more and more warheads in the same window of time. Eventually the system will reach a maximum number of targets destroyed and after this point all additional warheads will penetrate the defenses. This leads to several destabilizing effects.

First, a state that is not building similar defenses may be encouraged to attack before the system is in place, essentially starting the war while there is no clear advantage instead of waiting until they will be at a distinct disadvantage after the defenses are completed. Second, one of the easiest ways to counter any proposed defenses is to simply build more warheads and missiles, reaching that saturation point sooner and hitting targets through a strategy of attrition. Third, and most importantly, since defenses are more effective against small numbers of warheads, a nation with a defense system is actually encouraged to engage in a counterforce first strike. The smaller retaliatory strike is then more easily destroyed by the defense system than a full attack would be. This undermines the doctrine of MAD by discrediting a nation's ability to punish any aggressor with a lethal retaliatory second strike.

• Dead Hand, a Soviet nuclear retaliation system
• Decapitation strike
• Second strike
• Cuban Missile Crisis
• Preemptive war
• Mutual assured destruction
• No first use
• Nuclear terrorism

• Robert McNamara's "Mutual Deterrence" speech from 1962
• First Strike from the Dean Peter Krogh Foreign Affairs Digital Archives