Mattis Visit Defense Secretary James N. Mattis greets military leaders and vendors during Combat Lethality Technology Day at the Pentagon, May 25, 2018. DoD photo by Air Force Tech Sgt. Vernon Young Jr. SHARE: Download: Full Size (1.9 MB) Tags: science, technology, SecDef, James N. Mattis Credit: Vernon Young Jr. VIRIN: 180525-D-IO684-001C.JPG Photo Gallery