New Defense Secretary Chuck Hagel addresses Pentagon employees and service members during an all-hands call during his first day at the Pentagon, Feb. 27, 2013. Hagel earlier took the oath of office to serve as the 24th defense secretary. - New Defense Secretary Chuck Hagel addresses Pentagon employees and service members during an all-hands call during his first day at the Pentagon, Feb. 27, 2013. Hagel earlier took the oath of office to serve as the 24th defense secretary.