The U.S. military conducted a successful test flight of a hypersonic missile -- a significant milestone in the Defense Department's 16-year project to develop a conventionally armed, ultra-fast glide body designed for precision strike -- giving Pentagon leaders renewed confidence in a new weapon system slated for fielding in 2025 by the Army and Navy. In June, the Army and Navy apparently resolved engineering problems that for two years bedeviled efforts to rapidly field the Long-Range Hypersonic Weapon by launching...