The Japanese constitution—ironically imposed at US behest after World War II—states that "land, sea, and air forces, as well as other war potential, will never be maintained." Now Japanese warships participate in US military maneuvers in the Pacific. From AFP, June 22, via Spacewar:

A US warship successfully shot down a target missile warhead over the Pacific Thursday in a test of a sea-based missile defense system, the US military said. A Japanese destroyer performed surveillance and tracking exercises during the test, marking the first time any US ally has taken part in a US missile defense intercept test, the US Missile Defense Agency said.

The test came amid a confrontation with North Korea over its preparations to launch a long-range missile.

The sea-based system tested off Hawaii is designed to counter only short or medium range missiles, but the cruisers and destroyers that took part are capable of tracking long-range missiles as well.

The mock warhead was launched over the Pacific atop a medium range missile and destroyed in a direct hit six minutes later with an SM-3 missile fired by the Aegis cruiser USS Shiloh, the agency said.

"The missile successfully intercepted the target warhead outside the earths atmosphere more than 100 miles above the Pacific Ocean and 250 miles northwest of Kauai," the agency said in a statement.

"We are continuing to see great success with the very challenging technology of hit-to-kill, a technology that is used for all of our missile defense ground- and sea-based interceptor missiles," Lieutenant General Trey Obering, the agency chief, said in the statement.

He said it was the seventh successful intercept using the sea-based missile defense system out of eight tries.

The test came as the United States said Thursday that North Korea would have to pay a "cost" if it launched a long range missile.

The US has said that North Korea is preparing to launch a multi-stage Taepodong-2 ballistic missile with a range of up to 6,700 kilometers (4,200 miles). US reports have said a launch was imminent.

US defense officials said the United States was ready to use its missile defense system if necessary against any threatening launch.

A North Korean missile test "would be a provocation and a dangerous action which would have to have some consequences." He told lawmakers "there would be a reaction, and it would be a mistake for North Korea to do it."

South Korea's Defense Minister Yoon Kwang-ung said in Seoul that he did not believe a missile operation was imminent, but North Korea has received new warnings against making a launch.

Missile Defense Agency officials have said the missile interceptor test was long-planned and had nothing to do with North Korea's long-range missile launch plans.

But the agency's statement highlighted the role of the Japanese Aegis destroyer.

"This event marked the first time that an allied military unit participated in a US Aegis missile defense intercept test," it said.

It said the Japanese destroyer and a US Navy Aegis destroyer performed surveillance and tracking exercises during the test.

"This data can also be used to provide targeting information for other missile defense systems, including the ground-based long-range interceptor missiles now deployed in Alaska and California to protect all 50 states from a limited ballistic missile attack," the agency said.

A third Aegis destroyer used in the test linked up with a land-based missile defense radar to evaluate the ship's ability to receive and use target cueing data from missile defense command centers.

The mock warhead separated from the three-stage target missile. The direct hit marked only the second time a separating warhead has been successfully intercepted by a missile fired from an Aegis cruiser.

The cruisers use their modified Spy-1 radars and a shipboard battle management system to detect, track and target the warheads in space.

The SM-3 Block IA interceptor missile fired in Thursday's test is slated for deployment in the US Navy and had never been used before in an intercept test.

See our last posts on Japan and on North Korea.