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. Missile defense categories Missile defense can be divided into categories based on various characteristics: type/range of missile intercepted, the trajectory phase where the intercept occurs, and whether intercepted inside or outside the Earth's atmosphere: Type/range of missile intercepted These types/ranges include strategic, theater and tactical. Each entails unique requirements for intercept, and a defensive system capable of intercepting one missile type frequently cannot intercept others. However, there is sometimes overlap in capability. Strategic Targets long-range ICBMs, which travel at about 7 km/s (15,700 mph). Examples of currently active systems: Russian A-135 system which defends Moscow, and the U.S. Ground-Based Midcourse Defense system that defends the United States from missiles launched from Asia. Geographic range of strategic defense can be regional (Russian system) or national (U.S. system). Theater Targets medium-range missiles, which travel at about 3 km/s (6,700 mph) or less. In this context, the term "theater" means the entire localized region for military operations, typically a radius of several hundred kilometers. Defense range of theater defensive systems is usually on this order. Examples of deployed theater missile defenses: Israeli Arrow missile, American THAAD, and Russian S-400. Tactical Targets short-range tactical ballistic missiles, which usually travel at less than 1.5 km/s (3,400 mph). Tactical anti-ballistic missiles (ABMs) have short ranges, typically 20–80 km (12–50 miles). Examples of currently-deployed tactical ABMs: American MIM-104 Patriot and Russian S-300V. Trajectory phase Ballistic missiles can be intercepted in three regions of their trajectory: boost phase, midcourse phase, or terminal phase. Boost phase Intercepting the missile while its rocket motors are firing, usually over the launch territory. Advantages: Bright, hot rocket exhaust makes detection and targeting easier. Decoys cannot be used during boost phase. At this stage, the missile is full of flammable propellant, which makes it very vulnerable to explosive warheads. Disadvantages: Difficult to geographically position interceptors to intercept missiles in boost phase (not always possible without flying over hostile territory). Short time for intercept (typically about 180 seconds). Mid-course phase Intercepting the missile in space after the rocket burns