Patton led US forces in World War II, including as part of the Allied offensive across Europe after the Normandy invasion.

Mattis may remind Trump of Patton, but he can’t conduct the US military like Patton did. Mattis knows this, even if Trump’s early foreign policy forays show scant regard for history or statecraft and a dangerous propensity to extemporise.

Now he’s been confirmed, here’s a piece I wrote about new Def Sec James Mattis in December https://t.co/TIwP4Ny0TF @australian #Inauguration

— Travers McLeod (@TraversMcLeod) January 21, 2017

In November 2008, I travelled to Norfolk, Virginia, to interview Mattis, then commander of US Joint Forces Command and supreme allied commander for NATO.

I was researching the impact of law on US counter-insurgency operations in Iraq and Afghanistan. Three years earlier, the US had been described by Oxford academic Nico Krisch as a “lawless hegemon”. Not long afterwards, Mattis and general David Petraeus spearheaded a new approach through their counter-insurgency doctrine.

David Kilcullen, an Australian who advised Petraeus, called Mattis and Petraeus “an insurgency within the bureaucracy” that kept “pushing for change in the face of outright opposition”.

Any apprehension I felt about interviewing a general with a call-sign “Mad Dog” subsided once we met. Here was a genial man, softly spoken, who took each question on its merits and answered thoughtfully.

Mattis is a student of history, famous for giving soldiers thousands of pages of reading material before they deployed.

Counter-insurgency in Iraq, Mattis said, was only new “if we don’t read our own history”. But that didn’t mean they could “dust off” Cold War practices.

One historical text Mattis will know well is Carl von Clausewitz’s On War. The Prussian general and military theorist told us war has always been shaped by the “spirit of the age”.

This takes us back to Patton, and to Normandy. Mattis used that example to illustrate the changing character of war, especially the need for force to be used proportionately.

“When you look at the number of French people that our air and naval bombardment killed in Normandy to get those landing forces ashore, we just took the French villages of Sainte-Mere-Eglise and others, it was just the way of war. When you look at what we did to Dresden, we could never do something like that in today’s world,” said Mattis.

Mattis said the consequence of the “information age” for his soldiers was the need for them “to be able to explain what we are doing”.

Their ability to give a “compelling persuasive argument” that their values are the right values depends on being fluent in the laws of war, particularly where civilian casualties are involved.

For Mattis, “if the strategy is not sound, not ethically based, then the operation is going to have a challenge”.

One might be “doing the right thing on the battlefield” but “because of the immaculate conception of war that our laws bring with them”, unless civilian casualties can be explained in those terms there are real costs.

During operations in Afghanistan there was often a marginal delay, in one case just 17 seconds, between an incident occurring and it appearing on YouTube.

The approach championed by Mattis and Petraeus had no time for torture — a clear departure from the “fog of law” that existed in the early years of the Iraq and Afghanistan campaigns. Unlawful detention or interrogation practices were anathema to “living your values”. For Mattis, it was simple: “If you study history you recognise the reality of supremacy of an ethical approach.”

Words like that hardly marry with Trump’s campaign rhetoric, when he spoke about bringing back waterboarding and other forms of torture. When Trump met Mattis after the election, Mattis told him it wasn’t useful — he’d prefer using “a pack of cigarettes and a couple of beers”.

Unlike Trump, Mattis defended NATO during the campaign and knows the alliance intimately. He is suspicious of Iran but doesn’t support revoking the nuclear deal agreed by President Barack Obama.

As US allies work diligently to predict US actions, and reactions, after Trump’s inauguration, they are likely to be reassured by the figure set to head the Pentagon across the Potomac.

In Mattis, they can count on someone who will know their history, and the history of their alliance with the US. This assumes Mattis can successfully switch from being a general executing civilian orders to a civilian with control over the military.

This may be the most significant year in international relations since 1989.

Obviously, 2001 was a watershed because of 9/11 but reactions largely reinforced the existing international order.

This year is unmistakably different: the two countries most responsible for shaping the rules of the international system since World War II — the US and Britain — have voted to retreat from it. The timing, method and scale of their retreat is still unknown. That makes the situation only more precarious.

The last shift of this magnitude was probably in 1989, when the Berlin Wall fell and the Cold War came to an end.

Mattis will be conscious that the election of his commander in chief, not long after the Brexit vote, has few, if any, historical antecedents. But he will also be acutely aware that unlawful or disproportionate use of force by a great power has many, including in Iraq and Afghanistan barely a decade ago.

History is not on their side.

Mattis has made some hawkish statements, but is the right choice for an ahistorical president. With Petraeus, he changed the mindset of the US military.

Let’s hope that if duty and ethics call, Mattis can change the president’s mind, too.

This piece first appeared in The Australian on 5 December 2016 under the title Donald Trump’s ‘Patton’ has history in his corner.