President Barack Obama says the former Pentagon lawyer he is recalling to service to lead the Department of Homeland Security has a deep understanding of the threats and challenges facing the United States .
If confirmed by the Senate, Jeh Johnson would succeed Janet Napolitano, who is now president of the University of California system.
The 56-year-old Johnson was the Defence Department's top lawyer in Obama's first term. He returned to private practice last year.
At the Pentagon, Johnson oversaw the increased use of unmanned drone strikes, the revamping of military commission to try terrorism suspects and the repeal of the ban on gays in the military.
