If a North Korean nuclear-tipped missile makes it into the air, the U.S. and its allies have a response plan.

South Korea and Japan both rely on tiered missile defense. Stage two of South Korea’s three-stage defense system is the Korea Air and Missile Defense (KAMD) system, which is designed to intercept incoming missiles. To bolster that defense system, the U.S. recently began the process of deploying a THAAD (Terminal High Altitude Area Defense) battery to South Korea, after North Korea fired four missiles into the Sea of Japan.

China expressed concerns the THAAD X-band radar could be used to peer into its own territory, so the U.S. has agreed to configure THAAD in terminal mode in an effort to ease concerns. In terminal mode, the radar has a range of several hundred miles and can facilitate the elimination of missiles in the terminal phase of flight. THAAD can also be configured to forward-base mode, which extends the radar’s range so THAAD can target projectiles in the initial or launch phase.

China, nevertheless, continues to express opposition to the deployment.

THAAD is an important step for South Korean missile defense.

“THAAD is better than anything South Korea has or will have for decades,” Bruce Klingner, a senior research fellow for Northeast Asia at the Heritage Foundation who specializes in Korean and Japanese affairs, told The Daily Caller News Foundation. “It is imperative that we deploy it to augment the defense of Korea and the U.S. forces deployed there.”

There are also a number of Aegis destroyers operating in the waters off of South Korea. The U.S. has several in the region, Japan has six, and South Korea has three. The Aegis destroyer ballistic missile system can track multiple missiles simultaneously and intercept enemy projectiles as needed.

Gaps remain, however, in South Korea’s defense. For starters, South Korea’s KAMD is not incorporated into the broader allied defense system, which weakens its overall effectiveness. And the South is particularly vulnerable to submarine-launched ballistic missiles, which the North successfully tested last year.

Japan is much more “forward leaning” in its defense, Klingner notes. Japan has Patriot Advanced Capability (PAC)-2 and 3 systems, Aegis destroyers and SM-3 interceptors, and is considering deploying THAAD and Aegis Ashore units on Japanese soil to boost national defense.

The U.S. has ground-based midcourse defense systems in Fort Greely, Alaska and Vandenberg Air Force Base, California.

Anti-missile systems have their limitations though.

“Certainly, there is that possibility” that a nuclear-armed ballistic missile could slip through allied defenses, Klingner told TheDCNF, especially given that most regional missile defense systems have never been tested in actual battle conditions.

“Missile defenses help reduce the threat, but they can’t eliminate it,” Jeffrey Lewis, the director of the East Asia Nonproliferation Program at the Middlebury Institute of International Studies at Monterey, told TheDCNF.

In the simplest of terms, missile defense involves hitting a bullet with another bullet, which is no easy task.

“Missile defense systems will never provide 100 percent effectiveness … The addition of THAAD does not guarantee the protection of Seoul, but it does add another piece to the constantly changing puzzle of defense,” Rodger Baker, Vice President of Strategic Analysis at Stratfor, a geopolitical intelligence platform, told TheDCNF.

North Korea is rapidly developing the capabilities necessary to skirt allied ballistic missile defense systems.

“North Korea can probably build missiles (especially ER Scuds) faster and more cheaply than we can build and deploy defenses,” Lewis noted. In recent weapons tests and military drills, North Korea has practiced firing off multiple missiles in rapid succession or simultaneously to overwhelm enemy missile defense systems.

“This is a tactic called ‘salvo fire,’ which is designed to place greater stress on all types of ballistic missile defenses. I don’t know how many simultaneous attacks it would take to ‘saturate’ the battle-management systems in use today by the U.S., South Korean, or Japanese militaries, but the North Koreans seem determined to refine their salvo capabilities,” Joshua Pollack, editor of The Nonproliferation Review at the Middlebury Institute of International Studies at Monterey, told TheDCNF. “Even if it didn’t succeed in saturating the defenses, it would at least more rapidly deplete the defense, which has a limited number of shots.”

“Enough simultaneous launches could overwhelm the THAAD system and increase the risk of a nuclear-armed ballistic missile reaching its target in South Korea,” Kelsey Davenport, director of Nonproliferation Policy at the Arms Control Institute, told TheDCNF after North Korea launched three missiles at the same time last September.

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The simultaneous launch of multiple missiles is “basic missile defense countermeasure,” Lewis told CNN.

“One THAAD battery is not enough. We need at least two, if not many more,” he told TheDCNF.

“The good news is that if defenses hold up against the first salvo, it’s much easier to locate mobile missiles after they fire than before,” Pollack explained, adding: “Ballistic missiles are very hot and bright upon launch, so the point of origin can be detected by satellites very rapidly. Perhaps the empty North Korean missile launch vehicles could be hunted down before they have the chance to reload,” but there is no guarantee.

This article is based on a larger analysis of the prospects of nuclear fallout with North Korea published April 14.

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