The United States constantly emphasizes the high-tech nature and near-impenetrability of its deeply layered missile and air defense system. How realistic this is, and how the American missile defense system is structured — the one that supposedly will not allow anyone to destroy the United States — was examined by Military Affair.

To begin with, the American missile defense system is not built as a single «shield over the country» that automatically shoots down everything flying across the ocean. It is a complex network of satellites, radars, command posts, ships, ground-based systems and interceptors, each of which covers only its own part of the threat. The main feature of this system is that it was built not to repel a full-scale nuclear strike by an equal adversary, but primarily to defend against a limited launch of ballistic missiles from the territory of countries such as North Korea or Iran.

The logic of the American missile defense system is based on layering. A ballistic missile passes through several phases of flight: the boost phase, the midcourse phase, when warheads move through space by inertia, and the terminal phase, when they enter the atmosphere and head toward the target. In theory, interception is possible at each of these stages, but in practice each phase has its own limitations. During the boost phase, the missile is on foreign territory and is inaccessible to an interceptor. In the midcourse phase, in space, there is more time, but another problem arises: it is necessary to distinguish the real warhead from decoys and other missile defense penetration aids. In the terminal phase, the target is already closer and clearer, but the interception window becomes minimal.

The central element in protecting US territory from intercontinental missiles is the Ground-based Midcourse Defense system, or GMD. Its task is to intercept a limited number of ballistic missiles in the midcourse phase of their trajectory, that is, in space, before the warheads enter the atmosphere. For this purpose, ground-based GBI interceptors deployed in Alaska and California are used. The principle of destruction is kinetic: the interceptor must hit the target directly — a «bullet-to-bullet» strike. In reality, this is an extremely difficult task, because it is necessary not only to calculate the intercept point, but also to correctly determine which object among several radar tracks is the real warhead.

The GMD system is not just missiles in silos. It includes early warning, tracking radars, space-based sensors, a data transmission network and a command-and-control loop. First, satellites detect a missile launch by its infrared signature. Then ground-based and sea-based radars refine the trajectory, speed and expected impact area. After that, the command system must collect data from different sources, build a picture of the attack, calculate the intercept point and issue the launch command for the interceptor. Ideally, all elements work as a single organism: the satellite gives the early warning, radars refine the target, the command loop distributes the data, and the interceptor receives updates during flight.

The second important layer of the American missile defense system is the sea-based Aegis Ballistic Missile Defense system. It is installed on US Navy ships and on some allied ships, as well as in the ground-based Aegis Ashore version. Its main interceptors are SM-3 family missiles, designed to destroy ballistic targets outside the atmosphere, and SM-6 missiles, which can engage a range of air and missile threats inside the atmosphere. Aegis is especially important for regional missile defense: it protects bases and the fleet and can be deployed closer to a potential military crisis zone. However, after the successful SM-3 Block IIA test in 2020, Aegis also began to be considered as a possible supplement to the defense of US territory itself. But it is precisely a supplement, not a replacement for GMD.

The next echelon is THAAD. This is a mobile ground-based system designed to intercept short-, medium- and intermediate-range ballistic missiles in the terminal phase of their trajectory, in the upper layers of the atmosphere and beyond it. However, THAAD is not a full-fledged means of defending the entire US territory from an intercontinental nuclear strike. Its role is to cover the space below the strategic echelon and above traditional air defense. Put simply, THAAD is needed where the threat is already descending toward the target, but there is still a chance to destroy it at high altitude.

Even lower is the echelon with the Patriot PAC-3 system. It is closer to classic air defense and tactical missile defense. It is designed to destroy aircraft, cruise missiles and short-range ballistic missiles. Patriot is not intended to fight intercontinental warheads entering the atmosphere at enormous speed, but it is important for protecting troops, airfields, headquarters, urban areas and critical infrastructure from shorter-range missile threats. In the layered US defense system, Patriot plays the role of the last line of defense when a target has already broken through more distant layers.

A separate element of the American missile defense system is communications. Without it, even the most expensive interceptors turn into separate, disconnected systems. The main nerve center of the entire architecture is C2BMC, or Command and Control, Battle Management, and Communications. Its task is to combine data from satellites, radars, ships, ground batteries and command posts. In modern war, it is important not just to see a missile, but to quickly transmit information to the system that has the best chance of destroying it. This is especially difficult during a massive attack, when ballistic missiles, cruise missiles, drones and decoys are flying at the same time. In such a situation, missile defense becomes not so much a question of a single interceptor missile as a question of computational resilience, decision-making speed and the network’s ability not to go «blind» from overload.

The main technical problem of strategic missile defense is target discrimination. In the midcourse phase of flight in space, a warhead may fly alongside decoys, debris, mock-ups and other penetration aids. A radar sees a set of objects, but it must determine which one poses the real danger. If an interceptor is spent on a decoy, the defense will quickly exhaust its ammunition. That is why the United States is investing in more powerful radars, including the Long Range Discrimination Radar in Alaska, and in a new generation of NGI interceptors. Their purpose is not only greater speed or range, but also a better ability to operate against more complex targets.

Now comes the main question: can American missile defense intercept a nuclear strike? If this means a single or small-scale launch of intercontinental missiles by a state with a limited arsenal, there are hypothetical chances. In a scenario involving one or several launches, the system can fire several interceptors at one target, use data from different sensors and try to destroy the warhead in space. But even here there can be no talk of a 100 percent guarantee: real conditions are always more complicated than tests, and the failure of one element — a radar, communications link, sensor or the interceptor itself — can disrupt the interception.

If, however, the issue is a massive strike by Russia or China, the picture is fundamentally different. Such states have not only a large number of delivery systems and warheads, but also missile defense penetration aids: multiple reentry vehicles, decoys, maneuvering warheads, sea-launched missiles, cruise missiles, hypersonic systems and the ability to combine attack directions. The American missile defense system is not designed as an «absolute shield» against such a strike. It may try to intercept some targets, protect certain areas or reduce damage in a limited scenario, but it is completely incapable of reliably shielding the country from a full-scale nuclear strike.

An objective assessment of American missile defense must be two-sided. On the one hand, it is the most advanced and technologically saturated missile defense system in the world: early-warning satellites, global radars, ship-based Aegis, THAAD, Patriot, GMD, a unified command loop and constant modernization. No other country has such a combination of geography, fleet, allied network, sensors and industrial base. On the other hand, missile defense is not a magical protection against nuclear war. It is expensive, complex, dependent on the quality of intelligence and communications, tested under limited conditions and vulnerable to overload. In the nuclear sphere, even one warhead that gets through can mean catastrophe, so «partial effectiveness» is not the same as security.

Prospective American projects, including the Next Generation Interceptor and concepts for a new national missile defense shield, are aimed at eliminating the main weaknesses: improving target discrimination, increasing the number of interception attempts, expanding the sensor network and moving some capabilities into space. But here a new limit emerges — economic and strategic. The stronger American missile defense becomes, the more interested a potential adversary is in increasing the number of warheads, decoys and unconventional delivery systems, such as the Russian nuclear-powered Poseidon torpedo. As a result, the shield and the sword again enter a race of costs. The point is that an interceptor often costs more than the target, and for reliable protection, a reserve of interceptors must be not one-to-one, but significantly larger.

Therefore, the honest conclusion is this: American missile defense can increase US resilience against limited missile strikes, complicate adversaries' calculations and provide a chance of interception in specific scenarios. But against a major nuclear strike by an equal adversary, it is absolutely not a guaranteed shield and is unlikely to become one in the foreseeable future. Its real role is to reduce vulnerability, cover part of the threats and make an attack less predictable for whoever decides to press the button first.