In James “Mad Dog” Mattis, Donald Trump chose his idea of a perfect warrior to lead the Department of Defense. Whether Mattis, who’s known as a warrior rather than an administrator, and the job are a perfect fit remains to be seen.

The National Security Act of 1947 forbids military leaders from serving as secretary of defense until they have been a civilian for seven years. Mattis has only been out of the service for three and a half years, so he needed Congress to grant him a waiver from the prohibition, which it did—the first such waiver since General George C. Marshall in 1950.

During his confirmation hearing before the Senate Armed Services Committee and at other times, Mattis has taken several positions at odds with those of President Trump. Unlike Trump, he opposed the use of torture, expressed skepticism of Vladimir Putin’s reliability as a partner and gave full support of NATO, which he described as “the most successful military alliance certainly in modern world history, probably ever.”

Mattis was born September 8, 1950, in Pullman, Washington, to John and Lucille Mattis and grew up in nearby Richland. He attended Columbia High School, graduating in 1968. He then went to Central Washington State College, where he joined the Reserve Officers Training Corps. Mattis graduated with a B.A. in history in 1972 and was commissioned as a second lieutenant in the Marine Corps.

However, Mattis didn’t serve in Vietnam. Instead, he was put in charge of a stateside rifle platoon in the 3rd Marine Division. He served in other billets as he worked his way up the command structure, including heading a Portland, Oregon, recruiting office as a major, but didn’t see combat until much later in his career.

After a promotion to lieutenant colonel, Mattis led an assault battalion in the 1991 Gulf War. His was one of the first U.S. units into Kuwait.

By the time of the terror attacks on September 11, 2001, Mattis had been promoted twice; to colonel and subsequently to brigadier general. In the fall of 2001, Mattis was commander of the 1st Marine Expeditionary Brigade and was then given command of Task Force 58, which moved into southern Afghanistan in November of that year.

Mattis was promoted to major general and in 2002 assumed command of the 1st Marine Division, which he took into Iraq in March 2003. Immediately before the invasion, Mattis wrote a letter, a copy of which was given to each of his Marines. Part of it read: “You are part of the world’s most feared and trusted force. Engage your brain before you engage your weapon. Share your courage with each other as we enter the uncertain terrain north of the Line of Departure. Keep faith in your comrades on your left and right and Marine Air overhead. Fight with a happy heart and strong spirit.”

In contrast to Trump, who has said he’ll reinstitute the practice of waterboarding, Mattis gained a reputation for not tolerating the torture of prisoners. During a meeting with the President-elect, Mattis told Trump “Give me a pack of cigarettes and a couple of beers, and I do better with that than I do with torture.”

In 2003, Mattis visited a detention center that had been an Iraqi army barracks. There he found the body of a 52-year-old Iraqi who had been arrested in connection with the capture by Iraqi forces of Private First Class Jessica Lynch. The dead man was found to have been tortured via sleep deprivation and being forced to stand for long periods of time, and was beaten by his captors. Finally, as they dragged him outside, a bone broke in his neck, killing him.

Mattis banned torture in his units. Because of problems with the evidence, only two Marines were convicted in the case, both of lesser charges.

But Mattis didn’t come out of Iraq with his reputation intact. In 2004, Mattis led his Marines into Fallujah. There, hundreds of civilians were killed, and the local soccer stadium was pressed into service as a temporary graveyard because the Marines were camped out in the cemetery. Marines were also accused of shooting at ambulances, but later claimed weapons were seen being loaded into the vehicles.

Later that spring, Mattis ordered an attack on what turned out to be a wedding party in the Iraqi desert. Forty-two people were killed in the attack. Mattis said the party was in reality a group of insurgents. “How many people go to the middle of the desert…to hold a wedding 80 miles from the nearest civilization?” he told The Guardian. “These were more than two dozen military-age males. Let’s not be naive.” However, the Associated Press later found video of the event, which included scenes of the bride, other women, and children.

Some say Mattis’ conduct in Iraq amounted to war crimes. “There have been credible reports that U.S. troops under the command of Gen. Mattis did target civilians, conducted indiscriminate attacks and also conducted attacks against military objectives that caused disproportionate casualties to civilians during military operations in Fallujah,” Gabor Rona, who teaches international law at Columbia University and worked as a legal adviser at the Geneva headquarters of the International Committee of the Red Cross said at the time of the siege, according to Reveal.

“All of these are war crimes,” Rona said. “Applying the doctrine of command responsibility, Gen. Mattis would be responsible for these misdeeds, these war crimes of troops under his command if he…either knew, should’ve known or did nothing to prevent or punish this behavior.”

When Marines were found to have killed 24 civilians in Haditha in late 2005, Mattis, by this time stationed at Camp Pendleton in Southern California, was the convening authority for the courts martial. Instead of having those involved in the killings prosecuted, however, Mattis wrote letters of exoneration for several Marines. Only one man was ever punished for the killings, and it was a staff sergeant who was merely reduced in rank to private.

Mattis isn’t shy about his love of battle. In 2005, he said about fighting the Taliban: “Actually it’s quite fun to fight them, you know. It’s a hell of a hoot. It’s fun to shoot some people. I’ll be right up there with you. I like brawling.”

Mattis acquired the nickname “Mad Dog,” which he is said to dislike, after the second battle of Fallujah in 2004. A second nickname, “Warrior Monk,” came from his love of reading military history—he has a library of 7,000 books—and the fact that he’s never been married and is childless.

Mattis went on to lead the U.S. Joint Forces Command from 2007 to 2009 and then took over U.S. Central Command, which is responsible for U.S. forces from the Arabian Gulf into Central Asia, until his retirement in 2013.

Even Mattis’ departure from the Marine Corps wasn’t without controversy. He retired five months early, of his own accord by his account. However, there are reports that he was forced out because there was some evidence that Mattis wanted to go to war with Iran, believing that country was partnered with ISIS. The Iranian government has actually shown great antipathy toward ISIS and it’s unlikely the country would team up with the terrorist organization.

However, Mattis has said that the United States should not pull out of its nuclear deal with Iran. If that happened, he said, the U.S. would likely stand alone in levying sanctions against that nation.

Mattis still lives in his hometown; he even served on a jury trial there shortly after Trump’s election. Since his retirement, Mattis has been a visiting scholar at the Hoover Institution and sat on the board of General Dynamics and of Theranos, a blood-testing startup. Mattis resigned from the Theranos board after it was found the company’s tests put patients at risk.

Mattis also briefly considered running for president in 2016. Some conservative donors, fearing Trump might get the Republican nomination, considered backing Mattis as a third-party candidate. Mattis, however, declined to run.

On January 20, 2017, the day of Trump’s inauguration, the Senate voted 98-1 to confirm Mattis as secretary of defense and he was sworn in later in the day. The only senator to vote against his confirmation was Kirsten Gillibrand (D-New York), who objected to breaking the tradition of having a civilian in charge of the Pentagon.

-Steve Straehley

To Learn More:

Inside Trump Defense Secretary Pick’s Efforts to Halt Torture (by Sheri Fink and Helene Cooper, New York Times)

Did Defense Secretary Nominee James Mattis Commit War Crimes in Iraq? (by Aaron Glantz, Reveal)

James Mattis’ 33-Year Grudge Against Iran (by Mark Perry, Politico)

The Secret Movement to Draft General James Mattis for President (by Tim Mak, Daily Beast)

Trump to Nominate Retired Gen. James Mattis to Lead Pentagon (by Lolita C. Baldor, Associated Press)