President-elect Donald Trump stunned the Pentagon and the broader defense world by nominating Fox News host Pete Hegseth to serve as his defense secretary, tapping someone largely inexperienced and untested on the global stage to take over the world's largest and most powerful military.

The news was met with bewilderment and worry among many in Washington as Trump passed on a number of established national security heavy-hitters and chose an Army National Guard officer well known in conservative circles as a co-host of Fox News Channel's "Fox & Friends Weekend."

While some Republican lawmakers had a muted response to the announcement, others called his combat experience an asset or said he was "tremendously capable."

Hegseth's choice could bring sweeping changes to the military. He has made it clear on his show and in interviews that, like Trump, he is opposed to "woke" programs that promote equity and inclusion. He also has questioned the role of women in combat and advocated pardoning service members charged with war crimes.

In June, at a rally in Las Vegas, Trump encouraged his supporters to buy Hegseth's book and said that if he won the presidency, "The woke stuff will be gone within a period of 24 hours. I can tell you."

The 44-year-old Hegseth, a staunch conservative who embraces Trump's "America First" policies, has pushed for making the military more lethal. During an interview on "The Shawn Ryan Show" podcast, he said allowing women to serve in combat hurts that effort.

"Everything about men and women serving together makes the situation more complicated, and complication in combat, that means casualties are worse," Hegseth said.

And while he said diversity in the military is a strength, he said it was because minority and white men can perform similarly, but the same isn't true for women.

By opening combat slots to women, "we've changed the standards in putting them there, which means you've changed the capability of that unit," Hegseth said in the podcast interview.

Since then-Defense Secretary Ash Carter opened all combat roles to women in 2016, women have successfully passed the military's grueling tests to become Green Berets and Army Rangers, and the Naval Special Warfare's test to serve as a combatant-craft crewman — the boat operators who transport Navy SEALs and conduct their own classified missions at sea.

While Trump lauded Hegseth as "tough, smart and a true believer in America First," others were quick to point to the TV personality's lack of experience. Some suggested he could be Pentagon chief in name only as the Trump White House runs the department.

A number of other names floated as possible defense choices had included Rep. Mike Rogers, R-Ala., chairman of the House Armed Services Committee; retired Lt. Gen. Keith Kellogg; Sen. Joni Ernst, R-Iowa; and Robert Wilkie, a former Pentagon official who was head of the Department of Veterans Affairs in Trump's first term.

"There is reason for concern that this is not a person who is a serious enough policymaker, serious enough policy implementer, to do a successful job," said Rep. Adam Smith of Washington, the ranking Democrat on the House Armed Services Committee.

Mark Cancian, a senior adviser at the Center for Strategic and International Studies, said Hegseth's lack of senior national security experience makes it more difficult to get Senate confirmation.

"I think Trump was tired of fighting with his secretaries of defense and picked one who would be loyal to him," Cancian said.

Military officials said the choice came out of the blue. A senior military officer, who spoke on condition of anonymity because they were not authorized to talk to the media, said Hegseth's selection is raising concerns about whether he has the practical experience to manage a large department with an enormous budget.

The Defense Department has a budget exceeding $800 billion, with about 1.3 million active-duty troops and another 1.4 million in the National Guard, Reserves and civilian employees based worldwide.

If confirmed, Hegseth would face a daunting array of global crises, from the wars in the Middle East and Ukraine and the expanding alliance between Russia and North Korea to the growing competition with China. There is also the need to upgrade the complex U.S. missile and nuclear defense apparatus and ensure the defense industry can keep up with America's need for weapons systems.

Smith said that while Hegseth's combat experience is a plus, running the Pentagon requires a lot of other skill sets, and his nomination will need some time for consideration.

"What's your plan? What are you going to do? ... How can you assure us that that lack of experience, you know, isn't going to make it impossible for you to do the job?" Smith said. "I think those are questions that need to be answered over the next couple of months."

Even some Republicans in the Senate, who would vote on his nomination, had a subdued response.

North Carolina Sen. Thom Tillis called the choice "interesting." Indiana Sen. Todd Young, who served in the Marine Corps, said, "I don't know much about his background or his vision, so I look forward to learning more."

North Dakota Sen. John Hoeven said he's not surprised that Trump chose Hegseth because Trump is "close to him and likes him and trusts him."

"The guy's obviously tremendously capable, a great communicator," Hoeven said. "I look forward to getting to know him better."

House Speaker Mike Johnson, R-La., said Hegseth brings a lot to the table and will be "reform-minded in the areas that need reform."

Hegseth has been a contributor since 2014 for Fox News, developing a friendship with Trump, who made regular appearances on his show. He is the author of "The War on Warriors: Behind the Betrayal of the Men Who Keep Us Free."

"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. "Nobody fights harder for the Troops, and Pete will be a courageous and patriotic champion of our 'Peace through Strength' policy."