The choice of Mr. Hegseth, a dedicated supporter of the president-elect in his first term, is outside the norm of the traditional choice for the post.

© Sam Hodgson for The New York Times

The pounding that sailors’ brains take from years of high-speed wave-slamming in the Special Boat Teams can cause symptoms that wreck their careers — and their lives.

© Shaina O’Neal/U.S. Navy, via Department of Defense