SAN DIEGO (April 16, 2021) Acting Secretary of the Navy (SECNAV), the Honorable Thomas W. Harker, tours the �Hall of Heroes� aboard the Zumwalt-class guided-missile destroyer USS Michael Monsoor (DDG 1001). Harker visited Monsoor during the Fleet Unmanned System Integrated Battle Problem 21 exercise. (U.S. Navy Photo by Fire Controlman 2nd Class Hannah Dill)