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North Korea renewed its threat Friday to fire ballistic missiles in the direction of the American territory of Guam, following ominous earlier threats by the rogue regime to launch missiles topped with hydrogen bombs to wipe out cities on the continental United States.

We need to be prepared to defend against new North Korean missile launches – and there is a way to do this short of full-scale war.

One U.S. military option would be to deploy a special team of two or three guided-missile destroyers – ships especially equipped to target, track and shoot down ballistic missiles – to strategic locations off the North Korean coastline. The ships would be positioned outside the 12-mile internationally recognized maritime territorial limit, or at other locations that intelligence indicates would be effective.

Sources intimately familiar with the operations and deployments of those destroyers – and the vast capabilities of their top-secret ballistic missile defense systems – tell me such a plan could work. They say a similar strategy is one of the military options being considered at the Pentagon and at U.S. Pacific Command headquarters in Hawaii. At the very least, this action would increase the costs to North Korea of continuing its missile program.

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Erecting what amounts to a destroyer “fence” to contain North Korean missiles and knock them out of the sky might seem like a farfetched scheme. Can a handful of small warships really perform such a huge task?

America’s ballistic missile defense warships are outfitted with systems and weapons that have been proven in rigorous testing, including SM-3 missile interceptors. Since 2002, the Aegis combat system – a powerful weapons system used by the U.S. Navy that utilizes computer and radar technology to find, track and destroy enemy targets – has recorded 35 successful ballistic-missile intercepts in 42 test attempts. And in the last dozen tests, the SM-3s have only missed once.

While U.S. tests of our missile defense system are admittedly choreographed, the characteristics of a targeted ballistic missile in a test situation closely match those of a missile that has been deployed with bad intentions.

Nearly all of the tests pit a single U.S. missile interceptor against a single ballistic missile. Against an actual launch, the Navy could send up numerous interceptors, dramatically increasing its chances for a hit.

Up to now, North Korea has failed to prove it has the capability to launch and control a sufficiently large salvo of missiles to overwhelm a single Aegis ballistic missile defense ship, let alone two or three. Some experts speculate that North Korea, slowed as it is by international economic sanctions, might not develop that capacity until near the end of the decade or beyond.

The U.S. missile destroyers that could be formed into a team and used to knock down North Korean missiles overhead would be those outfitted with the latest version of the four-decades-old Aegis combat system. The newest series of upgrades was certified in January 2015.

All U. S. Navy destroyers and cruisers possess Aegis combat systems, which were first developed to protect ships – especially aircraft carriers – against air threats such as cruise missiles and aircraft.

However, ballistic missile defense requires different sensor settings, algorithms and missiles. Only 40 percent of the U.S. Navy’s Aegis-equipped destroyers and cruisers are designed for ballistic missile defense.

The ballistic missile defense ships depend on SM-3 missile interceptors to blow apart enemy ballistic missiles relatively soon after they enter what’s called flight midcourse, at their most vulnerable point where the atmosphere ends. This starts about 400 miles above the Earth’s surface and extends out to a few thousand miles.

SM-3s have no explosive warhead. Instead they work through sheer force, colliding with the targeted missile with the power of a 10-ton truck traveling 600 miles per hour. For very short-range missiles, SM-2 interceptors can potentially be used. New interceptors, called SM-6s, are being tested that are designed to hit longer-range ballistic missiles later in flight as they descend and re-enter the atmosphere.

Every ballistic missile defense destroyer has the capacity to launch up to 96 missiles. Each ship would have to retain some Aegis capacity for self-defense and that missile number would depend on the mission.

For argument’s sake, assume a destroyer making up part of the “fence” could aim 80 interceptors at a launched North Korean missile. That would mean two ships could unleash a fusillade of 160 missiles and three ships could fire 240. If North Korea were to triple its single-day launch rate, which with sanctions seems extremely difficult, it could possibly send a dozen missiles aloft. In that case, the odds still favor the Aegis interceptors.

Recently North Korea has focused mainly on short- and medium-range missile tests. The North has yet to prove it can launch an intercontinental ballistic missile armed with a payload that can reach the United States, despite its boasts.

If Pyongyang does deploy such missiles and they break though the fence created by U.S. ships and head toward America, the U.S. Air Force could meet them with a total of 36 ground-based interceptors launched from Fort Greely in Alaska and Vandenberg Air Force Base in California. Those interceptors have hit targets in 10 of 18 tests, including the last two in June 2014 and May this year.

To execute such an aggressive plan for an Aegis-ship ballistic missile defense, some parts of which appear to be already in the works, the U.S. would have to place even greater focus on ballistic missile defense missions. American fleet commanders will need to make sure destroyer captains improve their skill in basic seamanship – a proficiency called into question after the Navy recently lost two of its valuable ballistic missile defense destroyers in collisions with commercial ships.

An important step in making the fence operational would be for the U.S. to adopt rules of engagement that allow the Navy destroyers to shoot down North Korean missiles as soon as leave the country’s airspace. Current rules only allow for tracking and monitoring.

If an SM-3 misses, there’s little concern of collateral damage. The interceptor would burn up harmlessly as it reentered the Earth’s atmosphere. Even if an interceptor collided with a nuclear warhead there would likely be no nuclear explosion, experts say.

While North Korea could be counted on to rail at the “recklessness” of an Aegis interceptor taking out one of its missiles, the hornet’s nest would be stirred up far less than in the case of a U.S. invasion of North Korea’s territory or attack on a land target.  In the latter two cases, the North Korean reprisal might be catastrophic, inflicting heavy casualties in South Korea.

If the moment for the destroyer fence to show its capability ever arrives, the U.S. Navy will have to make absolutely certain its missile-killing missiles don’t miss. North Korea would only feel emboldened if its greatest adversary seemed not up to the task of backing up its rhetoric with effective action.
  
Of course, a destroyer fence is only a short-term fix. North Korea will build more missiles and it’s only a matter of time before more countries acquire such weapons.

In the longer term, the Navy should consider upgrading more ships for ballistic missile defense.  The Navy should also push forward an idea broached by shipbuilder Huntington Ingalls Industries to develop a missile-defense variant of the San Antonio-class amphibious transport dock ship that can be fitted out with a massive strategic antimissile battery of more than 400 interceptors or other missiles.

Similarly, more thought should be given to accelerating testing and deployment of systems that support and enable Aegis. These include the SBX-1 – a huge golf ball-shaped radar dome mounted on an oil platform that can track ballistic missiles – and additional satellites that can be used to track intercontinental ballistic missiles as they travel through space.

With bold use of proven, off-the-shelf missile-defense technology, the U.S. can turn the tables on Pyongyang, neutralizing its strategic missile threat without launching a war. The goal would be to buy enough time for cooler heads to prevail.