Hegseth's resume is so thin and his list of alleged personal issues so long that he makes an unusual pick to lead the world's biggest nuclear-armed military with about 2.9 million employees and an $850 billion budget.

He has never led a large organization. He served as a major in the National Guard but is better known for his work until recently as a host on Trump-friendly Fox News.

After his nomination, a slew of damaging testimony emerged about past heavy drinking and accusations of abusive behavior toward his second wife and one case of sexual assault.

Hegseth denies any wrongdoing and Trump has stood by him, telling reporters Friday: "Pete's a very, very good man."

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

Supporters say his deployments in Afghanistan and Iraq give him the insight to run the Pentagon better than the top brass typically considered for the job.

In his Senate hearings and media appearances, Hegseth has aggressively driven home the need to make the US military less "woke" and more "lethal." He has also focused on ending what he says has been lowering of standards to help women enter the military.

He calls the allegations of improper personal behavior against him "smears" but has said he will stop drinking alcohol if confirmed to head the Pentagon.

- Tricky Senate math -

Republicans hold only a thin majority in the Senate and two of the party's 53 senators -- Susan Collins and Lisa Murkowski -- are expected to vote against Hegseth, joining what is expected to be a unanimous "no" from Democrats.

That would still allow Hegseth to squeak through. If one more Republican voted against, it would make 50-50 -- with Trump's vice president, JD Vance, coming to break the tie.

On Thursday, the Senate confirmed John Ratcliffe to head the CIA, while a vote on Kristi Noem's nomination to lead Homeland Security is expected Sunday morning.

Focus then shifts to Treasury nominee Scott Bessent and Trump's pick for Transport, Sean Duffy.

Those votes are not expected to be difficult for the Republicans.

However, the divisions exposed by Hegseth's nomination will flare up again next week when three more of Trump's most contentious nominees enter the spotlight.

Kash Patel -- Trump's pick to lead the FBI -- goes before the Senate Judiciary Committee on Thursday, the same day as Tulsi Gabbard's hearing in front of the Senate Intelligence Committee.

Both are facing major questions over their character, judgement and previous positions -- including Gabbard's echoing of Kremlin talking points on Ukraine. They are not expected to get any Democratic support.

Thursday is likely to be a day of drama as the Senate holds the first of two scheduled confirmation hearings for Trump's Health Secretary nominee Robert F Kennedy Jr, who is likely to be grilled on his anti-vaccine statements and embrace of other conspiracy theories.