Pledging to "restore the warrior ethos" in the Pentagon, Hegseth in brief remarks thanked President Donald Trump for selecting him and Vice President JD Vance for his tie-breaking vote in the Senate that allowed his nomination to pass.

Vance's vote Friday evening was only the second time in history a vice president had to intervene to save a cabinet nominee and came after three Republicans -- including former leader Mitch McConnell -- cast ballots against Hegseth.

The razor-edge result underscored concerns about Hegseth, who takes over the Pentagon with war raging in Ukraine, the Middle East volatile despite ceasefires in Lebanon and Gaza, and as Trump expands the military's role in security on the US-Mexico border.

The 44-year-old is a former Army National Guard officer and Bronze Star recipient with previous deployments to Iraq, Afghanistan and Guantanamo Bay in Cuba.

Until recently, he worked as a co-host for Fox News -- one of Trump's favored television channels.

Hegseth has a combative media personality, fierce loyalty and telegenic looks -- common hallmarks in Trump's entourage.

Supporters say Hegseth's deployments give him the insight to run the Defense Department better than more experienced officials who would normally be considered for the job.

Speaking Saturday after his swearing in, Hegseth said he was thinking of "the guys that I served with on the battlefield, the men and women who I locked shields with and put my life on the line with."

"We're going to think about those warriors with every single decision that we make," he said.

In confirming him, Republicans brushed aside his lack of experience leading an organization anywhere near the size of the Defense Department -- the country's largest employer with some three million personnel.

They also approved Hegseth despite allegations of financial mismanagement at veterans' nonprofits where he previously worked, reports of excessive drinking, and allegations that he sexually assaulted a woman in California.

Trump has stood by him, telling reporters on Friday that he's "a very, very good man."

Asked during his confirmation hearing last week about criticism he has faced, Hegseth said there was a "coordinated smear campaign" against him, and that he is "not a perfect person, but redemption is real."

The thrice-married father of seven has frequently proclaimed his Christian faith, and began his remarks Saturday by saying "All praise and glory to God, his will be done."

He credited his successful nomination to "Jesus and Jenny" -- his wife.