The top U.S. military official responsible for defending the nation against a North Korean nuclear strike said he is "very concerned" about the Pentagon's ability to keep pace with Pyongyang's technical advances in developing long-range missiles and industrial capacity to expand its offensive fleet. Gen. Glen VanHerck, head of U.S. Northern Command, was asked by lawmakers about his confidence in the Ground-based Midcourse Defense system in light of North Korea’s launch today of a new intercontinental ballistic missile, described by...