President Barack Obama nominated top Pentagon lawyer Jeh C. Johnson Friday to replace outgoing Homeland Security Secretary Janet Napolitano.
The president praised Johnson, saying he possessed a "deep understanding of the threats and challenges facing the United States."
"He's been there in the Situation Room, at the table in moments of decision," Obama told reporters in the White House Rose Garden.
Johnson has spent most of his career in national security as a military lawyer.
He dealt with issues like ending the military's "Don't-Ask-Don't-Tell" policy, escalating the use of drone strikes during the wars in Iraq and Afghanistan, and changing military commissions to try terrorism suspects rather than using civilian courts.