In this Sept. 21, 2018, file photo, Defense Secretary Jim Mattis speaks during the 2018 POW/MIA National Recognition Day Ceremony at the Pentagon in Washington. Image Credit: AP

There are those that lead soldiers from the rear, and there are those that lead from the front. This anecdote from Stars & Stripes, the US military newspaper, will give you a pretty good indication where former Marine General James Mattis stood while serving for four decades in the American Marine Corps.

The story goes that it was Christmas Day in 1998 when the then Marine Commandant General Charles Krulak brought cookies to officers and other troops in the Washington area who had to stand duty then. When he walked in to surprise the officer on duty — which should have been a Major — he asked: “Who’s the officer of the day?”

“Sir, it’s Brigadier General Mattis,” the young lance corporal said.

After a brief back and forth where Krulak thought he might have been misunderstood, he said: “OK, so who was the officer who slept in that bed last night?”

“Sir, it’s Brigadier General Mattis,” the Marine said.

Then, General Mattis walked around the corner, in his duty uniform. He explained to Krulak that he took the major’s duty since he had a family at home, and Mattis didn’t.

“I’m a bachelor,” Krulak recalled him saying. “I thought why should the major miss out on the fun of having Christmas with his family, and so I took the duty for him.”

“That’s the kind of officer that Jim Mattis is,” Krulak said.

And that’s just one reason why the former general who is still the United States Defence Secretary — until New Year’s Eve, that is — is held in such high regard by friends and allies alike in a White House administration that is akin to a rudderless ship with a captain preoccupied by charting his own course in very turbulent seas.

For months, the relationship between the president and the secretary of defence has been severely strained, and the final straw for the principled Mattis came the week before Christmas when Trump announced that he would be withdrawing US troops from Syria, declaring that Daesh had been largely wiped out, and that the commander-in-chief would be drawing down troop levels in Afghanistan also.

Mattis is not a man prone to holding fire when circumstances demand action — and the decision to withdraw US troops from Syria was simply too much for the former general to bear. One can almost imagine him determined to say what needed to be said, rather like Jack Nicholson as Colonel Nathan Jessop in a Few Good Men flipping his lid, reminding those in a courtroom — or indeed in the Oval Office as he rages — “You can’t handle the truth!”

For Nato generals and leaders in capitals across Canada, Europe and beyond, Mattis was the last steadying hand on that tiller in Washington, or as that famous anonymous Opinion piece in the New York Times noted, one of the “last adults in the room”.

Mattis’ resignation letter so infuriated the commander-in-chief that instead of that resignation taking effect in February, the president ordered Mattis out by New Year’s Day, and probably with the rider not to let the door hit him on the way out. Indeed, the president had taken pride in surrounding himself with former military men, generals, and all of whom have now departed his orbit. Being under fire is one thing, being in the line of fire when there’s obvious chaos, a lack of discipline, no clear objectives and general disorder was more than enough for these military men.

Once considered among the most influential advisers to a president with no prior government experience, Mattis has been repeatedly overruled by Trump in recent months and left out of key discussions as the president pursued his own national security path. And that Trump referred to Mattis by his hated nickname of ‘Mad Dog’ didn’t help either.

Trump also sidestepped Mattis’ concern about deploying US forces to the US-Mexico border this autumn with only a vague mandate for border security. Mattis has told Pentagon leaders that he is following orders and they must do the same.

The 68-year-old retired general was second only to Trump in issuing blunt military threats to North Korea before the president’s abrupt decision in March to seek rapprochement through one-on-one diplomacy with North Korean leader Kim Jong-un. Mattis is said to be among the strongest sceptics about the pledge of denuclearisation that Trump claims he received from Kim at a summit in June.

“I see my generals — those generals are going to keep us so safe,” Trump said during a luncheon shortly after he was sworn in as president in January, 2017. “They’re going to have a lot of problems, the other side.”

He said the group of military men he had assembled were out of “central casting,” and he singled out Mattis.

“If I’m doing a movie, I pick you, General, General Mattis,” Trump told the audience.

In the beginning of the administration, Mattis maintained his influence with Trump even as he repeatedly argued against some of the president’s iconoclastic impulses — trying to explain with maps and charts how his decisions could hurt American interests. He often wove in discussion of international trade and US foreign aid, knowing that those subjects are likely to hold the president’s interest, officials said.

He is the highest-raking military officer to lead the Pentagon and has more than 40 years’ service commanding Marines in Iraq from 1993 onwards. His military call sign was “Chaos” and he’s known for some of his memorable quotes including: “Be polite, be professional, but have a plan to kill everybody you meet.” Hmmm.

— With inputs from agencies