The U.S. military on May 30 successfully tested a missile defense system that involved a simulated attack by an intercontinental ballistic missile, as North Korea aims to perfect an ICBM of its own. (Reuters)

The U.S. military destroyed a mock intercontinental ballistic missile hundreds of miles over the Pacific for the first time Tuesday, a step forward for a missile-defense program that has taken on new significance in light of North Korean threats.

The ground-based midcourse defense (GMD) system used a five-foot “kill vehicle” released from a larger ground-based interceptor missile to obliterate the mock ICBM, defense officials said. The mock threat was launched from the Ronald Reagan Ballistic Missile Defense Test Site in the Marshall Islands, and it was met by an interceptor launched from a silo at Vandenberg Air Force Base in California.

“The intercept of a complex, threat-representative ICBM target is an incredible accomplishment for the GMD system and a critical milestone for this program,” Navy Vice Adm. Jim Syring, director of the Missile Defense Agency, said in a statement. “This system is vitally important to the defense of our homeland, and this test demonstrates that we have a capable, credible deterrent against a very real threat.”

The test, originally scheduled for last year, was pushed back as the Missile Defense Agency made engineering changes to the interceptor, according to a report from the Government Accountability Office released Tuesday. The problems prompted the Pentagon’s top weapons tester, the Directorate of Operational Test and Evaluation, to assess last year that the ground-based midcourse system had demonstrated only limited ability to defend the country in part because of its low reliability.

Navy Capt. Jeff Davis, a Pentagon spokesman, said before the test Tuesday morning that its timing was not tied directly to recent tensions with North Korea, which include Pyongyang continuing to carry out nuclear and ballistic missile tests and threatening to attack U.S. bases both abroad and in the continental United States.

But “in a more broad sense,” Davis said, “North Korea is obviously one of the reasons why we have this capability.”

Davis played down the need for a successful test ahead of time.

“We improve and learn from each test, regardless of the outcome,” he said. “That’s the reasons we conduct them.”

The test was led by the Missile Defense Agency, and it also included the Air Force’s 30th Space Wing at Vandenberg and U.S. Northern Command, which oversees the defense of the United States at home.

The Pentagon declared the missile-defense system ready for combat in 2004, but its testing history has been mixed. Four of the nine missile-intercept tests prior to Tuesday had been a success, including the last one in June 2014.

In April, Navy Adm. Harry Harris, the chief of Pacific Command, told the House Armed Services Committee that North Korea is “clearly in a position to threaten Hawaii today” with a ballistic missile attack and that the Pentagon should consider adding new ballistic missile interceptors and defensive radar there as a result.

“I believe that our ballistic missile architecture is sufficient to protect Hawaii today, but it can be overwhelmed,” Harris said at the time. If the United States faced a wave of incoming ballistic missiles, he added, “someone would have to make a decision on which one to take out or not. So that’s a difficult decision.”

Everyday, North Koreans are told that the Americans are "imperialists" and North Korean children are taught that "cunning American wolves" want to kill them. To understand why, we need to go back to the Korean War. (Anna Fifield,Jason Aldag/The Washington Post)