The U.S. project to establish a second Aegis Ashore site in Europe -- beleaguered by construction problems that have delayed by five years plans to declare the system operational -- achieved an important benchmark this month when the Navy activated the radar and weapon system even as work to complete the physical structure in Poland continues. On June 7, the Missile Defense Agency and the Navy conducted an event called “Aegis Light Off” setting the project on a trajectory to...