North Korea continued to defy the protests of world leaders on Tuesday by launching what looks to be its first intercontinental ballistic missile. The symbolism of launching on America’s Independence Day was surely no accident, but the technical feat is more consequential. The speed of North Korea’s progress toward threatening the U.S. with a fleet of nuclear-tipped ICBMs requires an urgent response.

Tuesday’s missile, dubbed the Hwasong-14, has an estimated range of 6,700 kilometers, which puts Alaska within range. America’s...