JOINT BASE PEARL HARBOR-HICKAM, Hawaii (March 5, 2021) Chairman of the Joint Chiefs of Staff Gen. Mark A. Milley learns how submariners use sonar to track contacts aboard the Virginia-class fast-attack submarine USS North Carolina (SSN 777) during a tour. Milley toured the submarine and engaged with Sailors during his visit to Joint Base Pearl Harbor-Hickam. (U.S. Navy photo by Chief Mass Communication Specialist Amanda Gray)