Anti-ballistic missile in the context of "Multiple independently targetable reentry vehicle"

Missile defense is a system, weapon, or technology involved in the detection, tracking, interception, and also the destruction of attacking missiles. Conceived as a defense against nuclear-armed intercontinental ballistic missiles (ICBMs), its application has broadened to include shorter-ranged non-nuclear tactical and theater missiles.

China, France, India, Iran, Israel, Italy, Russia, Taiwan, the United Kingdom and the United States have all developed such air defense systems.

Under the Manhattan Project, the United States was the first country to manufacture nuclear weapons and is the only country to have used them in combat, with the bombings of Hiroshima and Nagasaki in World War II against Japan. In total it conducted 1,054 nuclear tests, and tested many long-range nuclear weapons delivery systems.

The United States currently deploys 1,770 warheads, mostly under Strategic Command, to its nuclear triad: Ohio-class submarines with Trident II submarine-launched ballistic missiles, silo-based Minuteman III intercontinental ballistic missiles, and B-2 Spirit and B-52 Stratofortress bombers armed with B61 and B83 bombs and AGM-86B cruise missiles. The US maintains a limited anti-ballistic missile capability via the Ground-Based Interceptor and Aegis systems. The US plans to modernize its triad with the Columbia-class submarine, Sentinel ICBM, and B-21 Raider, from 2029.

The Indian Ballistic Missile Defence Programme is an initiative to develop and deploy a multi-layered ballistic missile defence system to protect India from ballistic missile attacks. It was launched in 1999 after the Kargil War by the Atal Bihari Vajpayee government. Testing was carried out and continuing as of 2006, and the system was expected to be operational within four years according to the head of the country's missiles development programme, Vijay Kumar Saraswat.

Introduced in light of the ballistic missile threat from Pakistan and China, it is a double-tiered system consisting of two land and sea-based interceptor missiles, namely the Prithvi Air Defence (PAD) missile for High Altitude interception, and the Advanced Air Defence (AAD) Missile for lower altitude interception. The two-tiered shield should be able to intercept any incoming missile launched from 5,000 kilometres away. The system also includes an overlapping network of early warning and tracking radars, as well as command and control posts.

The Ground-Based Interceptor (GBI) is the anti-ballistic missile component of the United States' Ground-Based Midcourse Defense (GMD) system. It is designed to intercept intercontinental ballistic missiles.

A missile launch facility, also known as an underground missile silo, launch facility (LF), or nuclear silo, is a vertical cylindrical structure constructed underground, for the storage and launching of intercontinental ballistic missiles (ICBMs), intermediate-range ballistic missiles (IRBMs), or medium-range ballistic missiles (MRBMs). Similar facilities can be used for anti-ballistic missiles (ABMs).

The structures typically have the missile some distance below ground, protected by a large "blast door" on top. They are usually connected, physically and/or electronically, to a missile launch control center.

Fort Greely is a United States Army launch site for anti-ballistic missiles located about 100 miles (160 km) southeast of Fairbanks, Alaska. It is also the home of the Cold Regions Test Center (CRTC), as Fort Greely is one of the coldest areas in Alaska, and can accommodate cold, extreme-cold, and temperate-weather tests depending on the season. It is named in honor of Major General Adolphus Greely.

There was an earlier Fort Greely on Kodiak Island.

Kwajalein Atoll (/ˈkwɑːdʒəlɪn/; Marshallese: Kuwajleen [kʷuwɑzʲ(ɛ)lʲɛːnʲ]) is part of the Republic of the Marshall Islands (RMI). The southernmost and largest island in the atoll is named Kwajalein Island, which its majority English-speaking residents (about 1,000 mostly U.S. civilian personnel) often shorten to Kwaj /kwɑːdʒ/. The total land area of the atoll is just over 6 square miles (16 km). It lies in the Ralik Chain, 2,100 nautical miles (3,900 km; 2,400 mi) southwest of Honolulu, Hawaii.

The US Navy has hosted a naval base on Kwajalein Island since World War II. It was the final resting place of the German cruiser Prinz Eugen after it survived the Operation Crossroads nuclear test in 1946. In the late 1950s, the U.S. Army took over the base as part of their Nike Zeus anti-ballistic missile efforts, and since then the atoll has been widely used for missile tests of all sorts. Today it is part of the Ronald Reagan Ballistic Missile Defense Test Site, with various radars, tracking cameras, missile launchers, and many support systems spread across many islands. One of the five ground stations used in controlling the operation of the Global Positioning System (GPS) navigation system is located on Kwajalein. The Marshall Islands are a dependent nation through the Free Compact of Association with the United States, after their independence established in the 1980s from a U.N. Protectorate. The defense of the Kwajalein, and the Marshall Islands is the responsibility of the United States. The important missile test range has been a mutually agreed task, and many Marshalese work at the military bases.

The Anti-Ballistic Missile Treaty, also known as the ABM Treaty or ABMT, was a 1972 arms control treaty between the United States and the Soviet Union on the limitation of the anti-ballistic missile (ABM) systems used in defending areas against strategic ballistic missiles, which are used to deliver nuclear weapons. It was intended to reduce pressures to build more nuclear weapons to maintain deterrence. Signed in 1972, it was in force for the next 30 years. Citing purported risks of nuclear blackmail from a rogue state, the United States under the George W. Bush administration unilaterally withdrew from the treaty in June 2002, leading to its termination. In ICBM defense, the US has subsequently operated the Ground-Based Midcourse Defense ABM system based in Alaska and California, as well as the sea-based Aegis Ballistic Missile Defense System. Russia maintains the A-135 ABM system around Moscow, and has developed the S-500 missile system.

Under the terms of the original 1972 treaty, each party was limited to two ABM complexes, one for the nation's capital and one for an intercontinental ballistic missile silo field. Each ABM complex was limited to 100 anti-ballistic missiles and their launchers, two phased-array radars, and 18 smaller radars for early-warning. ABM missiles that were not static and ground-based were prohibited. In 1974, the limit was reduced to just a single ABM complex. The USSR chose to deploy the A-35 system around its capital Moscow, the US elected to deploy the Safeguard Complex around its ICBM fields of the Twentieth Air Force, although this was only operational for a year from 1974 to 1975. A 1997 treaty addendum permitted "theater missile defense": anti-ballistic missiles used against theatre ballistic missiles, as long as they were not tested against targets with velocities over 5 km/s, typical of ICBM terminal phase. Also in 1997, five years after the dissolution of the Soviet Union, its former member states Belarus, Kazakhstan, Russia, and Ukraine were established as successors to the USSR within the treaty, with one ABM system permitted between them.