Pete Hegseth conducts an interview on "Fox & Friends" at Fox News Channel Studios on August 9, 2019 in New York City. (John Lamparski/Getty Images via CNN Newsource)

(CNN) โ€” President-elect Donald Trump has chosen Pete Hegseth, a Fox News host and Army veteran, to serve as his secretary of defense.

Hegsethโ€™s selection was a surprise, as he was not among those considered as a likely pick by members of Trumpโ€™s team, sources familiar with the discussions told CNN.

Sources said that it came down to Trump having a longstanding relationship with Hegseth, noting that the president-elect always thought he was โ€œsmartโ€ and was impressed by his career. Trump also likes that Hegseth is a military veteran and the account of his service in his book, the sources said.

While Hegsethโ€™s name had not been on the initial shortlist, Trump was struggling to land on a choice for the job, and he liked Hegseth from Trumpโ€™s last term when he briefly considered him for leading the Department of Veterans Affairs before being warned that he may not get confirmed by the Senate, one source familiar said.

โ€œTrump also thinks he has the look,โ€ one source said.

Many people in Trumpโ€™s orbit were caught by surprise by his decision, the sources said. Hegseth didnโ€™t emerge as a top candidate for defense secretary until Monday, a Trump adviser said, with the Fox News host interviewing for the role over the last 24 hours.

Trumpโ€™s choice of Hegseth is a notable departure from his picks for defense secretary in his first term, when he selected a four-star general, James Mattis, and an Army secretary, Mark Esper, to lead the Pentagon. But Trump ultimately soured on both of those secretaries and was sharply critical of them after Mattis resigned and Esper was fired.

One defense official told CNN, โ€œEveryone is simply shocked.โ€ Another Pentagon official who was following the potential picks for defense secretary learned about the possibility of Hegseth only in the hours before the nomination and, like others who spoke on condition of anonymity with CNN, didnโ€™t know how to react.

Even some former Trump officials who have remained close to former colleagues and have been in touch with the transition were caught off guard. One former Trump official also said they were โ€œshockedโ€ by the selection and expect thereโ€™s going to be an effort to โ€œtake him down.โ€

Indeed, in choosing Hegseth, Trump has likely set off what could be his first contentious confirmation fight for a Cabinet pick. While Senate Republicans newly in the majority are likely to be deferential to Trumpโ€™s selections, Trumpโ€™s nominees can only afford to lose a handful of Republicans to win confirmation.

Alaska Republican Sen Lisa Murkowski said โ€œwowโ€ on Tuesday evening upon hearing Trump had picked the Fox News host to lead the Pentagon. Sen. Todd Young, a Republican of Indiana, who has been critical of Trump at times, said he wanted to learn more about the intended nominee.

โ€œI just donโ€™t know much about his background and his vision. I look forward to learning more. I want to give all of President Trumpโ€™s nominees fair opportunity to state their qualifications and their vision,โ€ he said.

North Carolina GOP Sen. Thom Tillis answered with one word: โ€œInteresting.โ€

In a statement announcing Hegseth, Trump praised his combat record as well as his tenure as a Fox News host and his bestselling book.

โ€œPete has spent his entire life as a Warrior for the Troops, and for the Country,โ€ Trump said in a Tuesday statement. โ€œPete is tough, smart and a true believer in America First. With Pete at the helm, Americaโ€™s enemies are on notice – Our Military will be Great Again, and America will Never Back Down.โ€

Hegseth has questioned women serving in combat

Hegseth has a long record in the military, serving in Afghanistan and Iraq.

He has also acted as an informal adviser to Trump for a number of years while he was in and out of office, Trump advisers told CNN. While Hegseth was considered for a number of positions in Trumpโ€™s first administration, he was ultimately passed over, they said.

But in Hegseth, Trump is likely to have a loyalist leading the department with which he had an often rocky relationship during his first term. The president-elect feuded with his first defense secretary, Mattis, who resigned in protest after Trump announced an immediate withdrawal of US forces from Syria. Esper, Trumpโ€™s other confirmed defense secretary, had openly warned about the threat of another Trump administration in the weeks leading up to the election.

Hegseth has criticized efforts to allow women into combat roles, accusing the military of lowering standards to allow women into those jobs.

Speaking about his book, โ€œThe War on Warriors,โ€ published this year, Hegseth said in a recent podcast he was surprised โ€œthere hasnโ€™t been more blowbackโ€ on the book, โ€œbecause Iโ€™m straight up just saying, we should not have women in combat roles.โ€

โ€œIt hasnโ€™t made us more effective, hasnโ€™t made us more lethal, has made fighting more complicated. โ€ฆ Weโ€™ve all served with women, and theyโ€™re great,โ€ Hegseth said last week onโ€œThe Shawn Ryan Show.โ€ โ€œBut our institutions donโ€™t have to incentivize that in places where, traditionally โ€” not traditionally, over human history โ€” men in those positions are more capable.โ€

Hegseth later added that he took issue specifically with women in โ€œphysical, labor-intensive type jobs,โ€ such as those with the Navy SEALs, Army Rangers, Army Special Forces, Marine Special Operations, and jobs such as those in infantry, armor, and artillery units.

โ€œIโ€™m talking about something where strength is the differentiator,โ€ he said.

Hegseth has also criticized the militaryโ€™s diversity programs, saying on the same podcast, โ€œWoke sh*t has got to go.โ€

โ€œEither youโ€™re in for warfighting and thatโ€™s it, thatโ€™s the only litmus test we care about,โ€ he said. โ€œYouโ€™ve got to get DEI and CRT out of military academies so youโ€™re not training young officers to be baptized in this type of thinking.โ€

A Fox News host

The president-elect is known to value how his message is delivered to television audiences, and the selection elevates the TV personality to a critical role in Trumpโ€™s second administration. Rep. Mike Waltz of Florida had been floated for the job, but Trump has since asked him to serve as his national security adviser.

Hegseth started with Fox News as a contributor in 2014 and was named the co-host of โ€œFox & Friends Weekendโ€ in 2017. Hegsethโ€™s deal with the network ended Tuesday, Fox News said.

โ€œHis insights and analysis especially about the military resonated deeply with our viewers and made the program the major success that it is today,โ€ Fox News said in a statement. โ€œWe are extremely proud of his work at FOX News Media and wish him the best of luck in Washington.โ€

The Princeton and Harvard grad also served as CEO for veterans advocacy organization Concerned Veterans for America and holds two Bronze Stars, according to Simon & Schuster, the company that published his 2017 book โ€œIn the Arena.โ€

Hegseth says he was removed from inauguration duty in 2021 because of what he described as a religious tattoo.

In his book, Hegseth wrote that he had served under former Presidents George W. Bush, Barack Obama, and Trump. His unit was tasked to work the inauguration of Joe Biden as well on January 20, 2021.

โ€œUltimately, members of my unit in leadership deemed that I was an extremist or a white nationalist because of a tattoo I have, which is a religious tattoo,โ€ Hegseth told Fox News during an interview promoting his book in June. Hegseth said the tattoo is a Jerusalem cross.

CNN has reached out to the National Guard for comment.

One day before Bidenโ€™s inauguration, the National Guard Bureau said it had removed twelve soldiers from inauguration duty following a security vetting process intended to ensure troops do not have any ties to extremist groups.

CNN reported in 2019 that Hegseth, while working at Fox News, privately encouraged Trump to pardon some United States servicemen accused of war crimes. Trump went on to pardon two service members and restore the rank of Navy SEAL Eddie Gallagher, who had been demoted. The controversial move went against the advice of then-Defense Secretary Esper and other senior military leaders who had told Trump that a presidential pardon could potentially damage the integrity of the military judicial system.

Trump has suggested his national security team would be tasked with reassessing the United Statesโ€™ posture toward Ukraine and Russia, China, Iran, and the simmering conflict in the Middle East. He has also said he regretted many of the people he put in senior roles when he won the White House in 2016 and was upset with officials who tried to thwart his often-impulsive demands and desires.

The president-electโ€™s relationship with Pentagon leadership was incredibly fraught in his first term, and the two men confirmed to serve as defense secretary under him have been hugely critical of Trump since leaving office.

CNN reported last week that Pentagon officials have been gaming out various scenarios as they prepare for an overhaul of the Defense Department under Trump. The president-elect has suggested he would be open to using active-duty forces for domestic law enforcement and mass deportations. He has also indicated he wants to stack the federal government with loyalists and โ€œclean out corrupt actorsโ€ in the US national security establishment.