The following is the Nov. 23, 2022, Congressional Research Service report, Defense Primer: Ballistic Missile Defense.
From the report
The United States has been developing and deploying ballistic missile defenses (BMD) to defend against enemy missiles continuously since the late 1940s. In the late 1960s and early 1970s, the United States deployed a limited nuclear-tipped BMD system to protect a portion of its U.S. land-based nuclear ICBM (intercontinental ballistic missile) force in order to preserve a strategic deterrent against a Soviet nuclear attack on the Homeland. That system became active in 1975 but shut down in 1976 because of concerns over cost and effectiveness. In the FY1975 budget, the Army began funding research into hit-to-kill or kinetic energy interceptors as an alternative—the type of interceptor technology that dominates U.S. BMD systems today.
In 1983, President Reagan announced an enhanced effort for BMD. Since the start of the Reagan initiative in 1985, BMD has been a key national security interest in Congress, which has appropriated well over $200 billion for a broad range of BMD research and development programs and deployment of BMD systems here and abroad.
The Missile Defense Agency (MDA) is charged with the mission to develop, test, and field an integrated, layered, BMD system (BMDS) to defend the United States, U.S. deployed forces, and U.S. allies and partners against ballistic missiles of all ranges and in all phases of flight. The FY2023 budget request is $24.7 billion for missile defense, $9.6 billion of which is for MDA.
Ballistic Missile Threats
After an initial powered phase of flight, a ballistic missile leaves the atmosphere and follows an unpowered trajectory or flight path before reentering the atmosphere toward a predetermined target. Ballistic missiles have an effective range from a few hundred kilometers (km) to more than 10,000 km. Short-range ballistic missiles (SRBMs) range from 300-1,000 km and are generally considered for tactical military use. Medium-range ballistic missiles (MRBMs) have a range from 1,000-5,500 km, although most are armed with conventional warheads and range less than 3,500 km. ICBMs range further than 5,500 km and are generally considered as strategic deterrent forces.
Most of the world’s ballistic missiles belong to the United States and its allies and partners; however, China and, in particular, Russia also have significant numbers of ICBMs. Russia continues to possess intermediate-range ballistic and cruise missiles (3,500-5,500 km), which led to the U.S. withdrawal from the 1987 Intermediate Nuclear Forces (INF) Treaty. The 2022 Missile Defense Review additionally identifies ballistic missile threats from North Korea and Iran.
North Korea likely has an arsenal of hundreds of SRBMs that can reach all of South Korea and perhaps dozens of MRBMs (whose reliability at this point remains uncertain), capable of reaching Japan and U.S. bases in the region. North Korea has flight-tested two types of road-mobile ICBMs that have the range to strike the U.S. homeland. The Defense Intelligence Agency (DIA) has assessed that “North Korea’s continued development of ICBMs, IRBMs, and [submarine-launched ballistic missiles] demonstrates its intention to bolster its nuclear delivery capability.”
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