WASHINGTON (NewsNation Now) — President-elect Joe Biden Wednesday introduced retired Army Gen. Lloyd Austin as his nominee secretary of defense, amid concern from some in Congress that the Pentagon should be led by a civilian rather than a career officer.

Austin, who would be the country’s first Black secretary of defense, has built a reputation as an intensely private man who avoided the spotlight during a distinguished four-decade career in uniform, including a stint as head of the military’s Central Command, which oversees U.S. troops across the Middle East.

President-elect Joe Biden says he is asking Congress for a waiver to allow for the confirmation of retired four-star Army general Lloyd J. Austin as secretary of defense because the moment calls for it.

Biden said Wednesday in Wilmington, Delaware, that he “would not be asking for this exemption if I did not believe this moment in our history didn’t call for it. It does call for it.”

If confirmed by the Senate, Austin would need to obtain a congressional waiver to serve as defense secretary. Congress intended civilian control of the military when it created the position of secretary of defense in 1947 and prohibited a recently retired military officer from holding the position. Austin retired in 2016.

Biden said there is “no doubt” in his mind that Austin will “honor, respect and on a day-to-day basis breathe life into the preeminent principle of civilian leadership over military matters in our nation.”

Biden argued that Austin would work to put the civil-military balance “back on track.” He said the main reason he picked Austin was because he reacts well under pressure.

After Biden’s official introduction of Lloyd Austin as his secretary of defense pick, Austin took to the podium and said he reveres the principle of civilian control of the military.

He went on to say he understands the need for civilian control of the military and sees himself as a civilian, not as a general.

He said that if confirmed by the Senate, he will surround himself in the Pentagon with civilian officials and advisers to ensure accountability.

Austin was an unexpected choice. Most speculation centered on Michele Flournoy, an experienced Washington hand and Biden supporter. She would have been the first woman to run the Pentagon. Flournoy issued a statement Tuesday congratulating Austin and calling him a man of deep integrity.

Austin is widely admired for his military service, which includes leading troops in combat in Iraq and Afghanistan and overseeing U.S. military operations throughout the greater Middle East as head of Central Command. But the requirement for a congressional waiver makes getting him installed as Pentagon chief more complicated than usual. Austin retired in 2016 after 41 years in the Army and has never held a political position.

Such a congressional waiver has been granted only twice: in 1950 for George Marshall and in 2017 for Mattis. Some prominent Democrats opposed the Mattis waiver, and among those who voted for it, Sen. Jack Reed of Rhode Island expressed doubts.

“Waiving the law should happen no more than once in a generation,” Reed, the ranking Democrat on the Senate Armed Services Committee, said then, adding, “Therefore, I will not support a waiver for future nominees.”

Asked Tuesday about an Austin waiver, Reed seemed open to the possibility.

“I feel, in all fairness, you have to give the opportunity to the nominee to explain himself or herself,” he told reporters.

Sen. James Inhofe, R-Okla., the current chairman of the Armed Services Committee, said he had no problem voting for the waivers. “I always support waivers,” he said. But he said he doesn’t know Austin well.

Civilian control of the military is rooted in Americans’ historic wariness of large standing armies with the power to overthrow the government it is intended to serve. That is why the president is the commander in chief of the armed forces, and it reflects the rationale behind the prohibition against a recently retired military officer serving as defense secretary.

Democratic Sen. Richard Blumenthal of Connecticut said despite the historic nature of the nomination, he would not vote for a waiver because it “would contravene the basic principle that there should be civilian control over a nonpolitical military.”

“That principle is essential to our democracy … I think (it) has to be applied, unfortunately, in this instance,” he said.

Rep. Elissa Slotkin, a Michigan Democrat, said she has mixed feelings, including deep respect for Austin, with whom she worked as a Pentagon official during his years in Iraq and Afghanistan.

“But choosing another recently retired general to serve in a role that is designed for a civilian just feels off,” she said. “The job of secretary of defense is purpose-built to ensure civilian oversight of the military.”

Biden has known Austin at least since the general’s years leading U.S. and coalition troops in Iraq while Biden was vice president. Austin was commander in Baghdad of the Multinational Corps-Iraq in 2008 when Barack Obama was elected president, and he returned to lead troops from 2010 through 2011.

Austin, a 1975 graduate of the U.S. Military Academy at West Point, served in 2012 as the first Black vice chief of staff of the Army. A year later he assumed command of Central Command, where he fashioned and began implementing a strategy for rolling back the Islamic State militants in Iraq and Syria.

On Tuesday as he introduced members of his public health team, Biden vowed to distribute 100 million vaccines in his first 100 days and to make reopening schools a “national priority.” He again implored Americans to wear masks to slow the spread of the virus.

Biden’s health and human services secretary nominee, California Attorney General Xavier Becerra, will help oversee the government’s response to the pandemic, which has killed more than 283,000 in the United States.

Biden also plans to nominate Marcia Fudge, a Black congresswoman from Ohio, as his housing and urban development secretary, and Tom Vilsack, the former Iowa governor, as agriculture secretary, according to news reports. Vilsack held the same role during the Obama administration.