President-elect Donald Trump has announced he will nominate Army National Guardsman and Fox News host Pete Hegseth to serve as Secretary of Defense in his upcoming cabinet.

"Pete is tough, smart and a true believer in America First. With Pete at the helm, America’s enemies are on notice - Our Military will be Great Again, and America will Never Back Down," Trump said in a statement on the nomination.

Hegseth has served in the Army National Guard since 2003. He served with his unit at Guantanamo Bay in Cuba, volunteered to serve in Iraq and was also deployed to Afghanistan. He currently holds the rank of Major.

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Hegseth was also the executive director of the conservative policy organization Vets for Freedom from 2007 until 2012. He was then executive director for Concerned Veterans for America, another conservative veterans advocacy group, until 2015.

Hegseth ran to represent Minnesota in the U.S. Senate in 2012, but ended his campaign before that year's primary election.

Hegseth began working for Fox News in 2014 and is a co-host on "Fox & Friends Weekend."

The Senate will have to confirm Hegseth's nomination.

This is a developing story and will be updated.