As Gen. Lloyd J. Austin III retired from the Army four years ago, he reflected on a career that included years in Iraq. The toughest days, he said, came when troops whom he oversaw were killed in action.

“When you lose them, their loss affects you profoundly,” Austin said somberly. “Indeed, it stays with you forever.”

Austin, 67, was speaking in the language of loss that President-elect Joe Biden, whose son Beau died of cancer in 2015, often uses. The two men have known each other for years, with Austin deploying repeatedly in a war that Biden voted to authorize as a senator, and commanding troops in Iraq in 2008 and early 2009 as Beau was deployed on his staff.

On Sunday, Biden met with Austin and offered him the job of defense secretary in his administration, according to officials familiar with the decision. If he is confirmed to the position, he will become the first Black defense secretary in U.S. history.

At his retirement ceremony in 2016, Gen. Lloyd J. Austin III said that he loved his life in the military and would do it all again. (The Washington Post)

“He is a true and tested soldier and leader,” Biden said Tuesday in an essay in the Atlantic explaining his decision. “I’ve spent countless hours with him, in the field and in the White House Situation Room. I’ve sought his advice, seen his command, and admired his calm and his character. He is the definition of a patriot.”

The president-elect praised Austin’s decency and his career as a trailblazer, which includes becoming the first Black officer to command a division and corps of soldiers in combat and the first to oversee a theater of war.

Biden also was taken with Austin’s experience comforting grieving military families and his understanding of the human costs of war, said one person familiar with the decision, who like others spoke on the condition of anonymity because of the sensitivity of the issue.

Austin developed a personal relationship with Beau while they were both deployed, a second official familiar with Biden’s decision said. The two Catholics attended Mass together and sat next to each other almost every Sunday on deployment.

“They developed a deep relationship and even saw each other after Beau returned from his deployment,” the official said of Austin’s interaction with Biden’s son.

Austin’s selection is not without challenge.

As a recently retired military officer, he will require additional votes in the House and Senate. He also will face questions about China, after spending most of his career focusing on other issues, and questions about past U.S. failures in the Middle East.

In picking Austin, Biden appears to have bypassed Michèle Flournoy and Jeh Johnson, civilians who served in senior Pentagon roles during the Obama administration and have lengthy records of government service in their own right. They, too, have children who joined the military, according to past public comments.

But Biden and Austin have talked for years, including on Biden’s trips to Iraq as vice president. President Barack Obama entrusted the Iraq portfolio to Biden in 2009, as Austin served as the three-star commander of 152,000 coalition troops there. Austin later advanced to become the top U.S. commander in Iraq as the United States withdrew its forces in 2011, the vice chief of staff of the Army, and the chief of U.S. Central Command.

“He’s a uniquely qualified individual,” said Dana Pittard, a retired two-star Army general who served under Austin in Iraq after the United States launched operations against the Islamic State in 2014. “He’s a natural introvert, but he thinks through decisions and gets input from everyone, not just his close-in advisers.”

Austin will require a congressional waiver to overcome a law that states that no individual can become defense secretary within seven years of serving in the military. The restriction is designed to create separation between the civilian defense secretary and the generals they must oversee, and ensure that civilians are in charge of the Defense Department.

Exceptions have been granted only twice — to retired five-star Gen. George Marshall in 1950, and to retired Marine Gen. Jim Mattis in 2017.

“I have deep respect for Gen. Lloyd Austin. We worked together when he commanded U.S. forces in Iraq, when he was vice chief of the Army, and when he was the CENTCOM commander,” tweeted Rep. Elissa Slotkin (D-Mich.), a former defense official in the Obama administration. “But choosing another recently retired general to serve in a role designed for a civilian just feels off.”

Austin also has a reputation for caution that is appealing to some and frustrating to others.

As a senior officer, he was known for his detailed preparation, lack of engagement with the media and private nature.

“In the Principals Committee and National Security Council meetings I’ve been in, he was almost the most silent,” said a former U.S. official, referring to the high-level White House meetings where big foreign policy decisions are made.

Austin’s fellow generals similarly emphasized his meticulousness and reluctance to share his thoughts even in private settings. One former general recalled meeting regularly with Austin for what were supposed to be informal sessions in which the two high-ranking officers, both commanders in Iraq, could trade insights and test out ideas.

Austin would detail his main points without deviating from his notes.

“He was responsible for the lives of tens of thousands of Americans and wanted to make sure that the decisions he was taking were correct and consistent,” the former Army general said. “But it struck me as odd.”

Austin could face questions about the rise of the Islamic State and early U.S. stumbles to counter the group in 2014. While he sought to keep some 24,000 troops in Iraq after 2011, according to a U.S. Army history of the war, he was overruled, quietly carried out the withdrawal instead and watched three years later as militants seized Iraqi cities.

Austin also could face scrutiny for his ties to Raytheon, a major defense contractor. After retiring, he joined the company’s board of directors. Other defense secretary candidates have also had ties to the defense industry.

A native of Mobile, Ala., Austin grew up as one of six children in the rural southwestern Georgia town of Thomasville. He was accepted into University of Notre Dame but nudged by his father, a retired postal worker, into accepting an offer at the U.S. Military Academy at West Point, N.Y., he said during his retirement ceremony.

Austin graduated in 1975, planning to serve five years and then go to law school, he later recalled. Instead, he worked his way up the ranks while earning master’s degrees in education and business, serving nearly 41 years.

A towering man well over 6 feet tall, he earned a reputation for leading thoughtfully and without screaming, said Alex Brown Jr., a former Army sergeant who served in a battalion commanded by Austin at Fort Bragg, N.C., in the 1990s.

Brown recalled one time when a soldier under his supervision was written up for misbehavior and that Brown had avoided dealing with the soldier’s outburst because Brown was off-duty at the time and had been drinking alcohol.

“I just remember him listening to everything that happened, and he dealt fairly with that soldier,” said Brown, who is now a schoolteacher in Louisville. “Then he told me that, as a leader, you never have the option to opt out. So, if alcohol is going to prevent you from doing that, you need to consider that. I’ll always remember that.”

Austin became the one-star assistant commander for maneuver of the 3rd Infantry Division, of Fort Stewart, Ga., two months before the 9/11 terrorist attacks and played a key role in the U.S. invasion of Iraq in March 2003.

The division participated in “Thunder Run” strikes on Baghdad, in which infantrymen and tanks launched rapid operations. The city fell quickly, and Austin received a Silver Star — two steps down from the Medal of Honor in recognizing valor in combat — for his actions.

In 2008, Austin returned to Iraq as the commander of Multinational Corps-Iraq as it was beginning to withdraw troops. He oversaw combined efforts with Iraqi forces to seize control of Basra and Sadr City from militants, and then returned for a stint on the staff of Adm. Mike Mullen, the chairman of the Joint Chiefs of Staff.

He was back in Iraq as the top U.S. commander in September 2010. Initially, he sought to keep a residual force of at least 24,000 soldiers in Iraq beyond 2011 to prevent any resurgence of what eventually would become the Islamic State.

Jim Jeffrey, who served as U.S. ambassador in Iraq from 2010 to 2012, said he and Austin jointly led the effort to convince top officials in Washington of the need to secure a residual force, when an earlier U.S.-Iraqi agreement specified that all American troops would leave. Austin’s plan was reduced to 10,000, then 5,000, following talks with officials in Washington, Jeffrey said.

“He would have preferred, I believe, a larger number,” Jeffrey said. “But he was happy to push for the number that the Obama administration settled on.”

Jeffrey said he and Austin then made the case to Iraqi officials and lawmakers for the country’s parliament to approve an American presence beyond the end of that year. They balked at doing so, so Austin pivoted to overseeing a rapid military withdrawal from Iraq, a major logistical undertaking executed in the space of a few months.

As the United States attempted to counter the Islamic State, Austin faced criticism from lawmakers as a $500 million effort to train Syrian rebels to fight the Islamic State failed. Sen. John McCain (R-Ariz.), chairman of the Armed Services Committee, told Austin that early efforts were an “abject failure” and that his testimony was “divorced from the reality of every outside expert.”

Ashton B. Carter, Obama’s defense secretary at the time, offered a similar assessment in a memoir. A plan that Austin offered to him to retake the city of Mosul from the militants “was entirely unrealistic, relying on Iraqi army formations that barely existed on paper, let alone in reality,” Carter wrote.

By the time Austin retired in spring 2016, the United States had rolled back major Islamic State gains in collaboration with Iraqi and Syrian forces.

Gen. Mark A. Milley, now the chairman of the Joint Chiefs of Staff, described him as a national treasure, but Austin deflected praise.

“Ladies and gentlemen, I will hang up my uniform for the last time later today, and the fact is I have only known one life and that is the life of a soldier,” he said. “Given the chance, I would do it all again — in a heartbeat.”

Annie Linskey, Missy Ryan, Paul Sonne and Greg Jaffe contributed to this report.