Lt. Gen. HR McMaster to remain active duty as national security adviser

McMaster is an Army lieutenant general.

Trump said Pence played a role in McMaster's selection and a Pence adviser said the vice president participated in the search.

"That combination is something very, very special," Trump said of McMaster and Kellogg.

Retired admiral and Navy SEAL Robert Harward, an ABC News contributor, was offered the job after Flynn's departure but turned down the position for personal reasons, according to a senior administration source.

McMaster, a West Point graduate who hold a Ph.D., was awarded the Silver Star for his leadership in the Gulf War. He is considered a leader in strategic thinking and was instrumental in counterinsurgency during the Iraq War.

McMaster isn't the first NSA to remain on active military duty during his term. Brent Scowcroft did under Gerald Ford as did Colin Powell under Ronald Reagan.