Analyses of recent North Korean flight tests and missiles paraded through the streets of Pyongyang suggest that the North may also be seeking to develop maneuverable warheads. Such a tactic, if successfully developed, would help warheads dodge antimissile interceptors.

For that reason, President Barack Obama ordered in 2014 that the traditional missile defenses be supplemented by a covert program intended to sabotage launches before they happen. That program includes electronic warfare attacks, but it is unclear how successful it has been. Experts say that a combination of that “left of launch” sabotage, so called because it comes before or just as a missile launches, and “right of launch” interception of airborne missiles, the kind practiced on Tuesday, represent the best chance of protecting the United States.

Efforts to test the country’s multibillion-dollar efforts at missile defense have had mixed results. A Pentagon report in January criticized the long-range system, saying that it “demonstrates a limited capability to defend the U.S. homeland from small numbers” of medium- and long-range missiles “launched from North Korea or Iran.”

In nine of the 17 tests of the system since 1999, the target missile was not destroyed, officials said. Critics of the system say the test record has not improved over time, as would be expected for a system that is maturing. And “the tests have still not been done under realistic conditions,” Laura Grego, a physicist with the Union of Concerned Scientists, wrote in a blog post on Monday.

Ms. Grego and other scientists argue that only when the system is tested in a range of situations — such as at night, or when an adversary is using countermeasures — would the Defense Department be able to say that it works.

Tuesday’s test was launched from Kwajalein Atoll in the Marshall Islands. Because the location was known and the approximate time of the launch was planned, the interceptor was ready — which might not be the case under real conditions.