Rexon Ryu, who is partly of Korean descent, has been named the new chief of staff at the U.S. Defense Department.
Ryu's father is Korean and mother is American. He was born in California and served as an aide to Chuck Hagel when the defense secretary was a senator from 2005 to 2009.
Foreign Policy magazine cited a source as saying Ryu "knows the Hill, and most importantly, he understands the way the secretary thinks and meshes well with his leadership style."
From 2011, he was the deputy to the U.S. permanent representative to the UN.
He will start his new job early next month. Hagel said he has depended on Ryu's insight into national security for a long time.
A senior Pentagon official said Ryu faces plenty of challenges overseeing the department's response to the civil war in Iraq, Ukraine crisis, territorial disputes in the South China Sea and other issues.
He will be replacing Mark Lippert, who has been appointed U.S. ambassador to Korea and is awaiting Senate confirmation.