JOINT BASE PEARL HARBOR-HICKAM (June 2, 2021) Sailors assigned to the Los Angeles-class fast-attack submarine USS Columbia (SSN 771) load a Mark 48 advanced capability torpedo for Exercise Agile Dagger 2021 (AD21). AD21 is a training exercise, with one-third of the Pacific Submarine Force getting underway, to assess warfighting readiness and build capacity for the joint force. (U.S. Navy photo by Mass Communication Specialist 1st Class Michael B. Zingaro)