JAMES MATTIS, America’s defence secretary, is a man who weighs his words. He is a reader, earning fame in the Marine Corps for carrying works of Roman military history into warzones in his rucksack, even as he earned a simultaneous reputation for ferocity in combat. He speaks sparingly in public, rarely appears on television and turns positively mulish when asked by reporters to comment on breaking news on which he has not been briefed.

It matters, then, that when Mr Mattis—a former four-star general turned civilian head of the most powerful armed forces on earth—visited the border between South and North Korea on October 27th, his brief statement revolved around a quote from America’s top diplomat, Rex Tillerson: “Our goal is not war.”

Mr Mattis spoke of peace, stability and of the value of the 60-year old alliance between South Korea and America—an “ironclad commitment”, he called it. Standing yards from North Korea in the eerie Cold War stage-set of the truce village at Panmunjom, he did not bang the drums of war, or threaten to destroy North Korea if attacked, as President Donald Trump has done. Nor did Mr Mattis address himself directly to Kim Jong-Un, the young, hereditary despot mocked by Mr Trump as “Little Rocket Man”. Mr Mattis sent just one overt signal to Mr Kim, whose sentries watched the defence secretary from a distance of less than 20 feet, heavy steel helmets sitting awkwardly atop their slight frames, their green-brown uniforms badly cut and baggy.

At the end of his brief statement the American defence secretary shook the hand of his counterpart Song Young-moo, in a familiar show of unity—what Fleet Street photographers call a “grip and grin”. But as cameras on the Southern side clicked furiously, Mr Mattis murmured to Mr Song that they should turn and shake hands while facing the northern side, their only visible audience a group of four sentries from the Korean People’s Army (KPA), one of whom was silently filming proceedings.

Mr Song, it is reported by the South Korean press, wanted a still more dramatic show of armed unity. A retired admiral, he had offered to wear his naval uniform if Mr Mattis wore the combat uniform of a marines general. That was never likely to happen: Mr Mattis may carry himself like a general and makes a point of talking to the troops like a visiting officer, but he is wont to stress that America is a country with civilian control of the military.

The words used by Mr Mattis were in a sense diplomatic boilerplate. American presidents, cabinet secretaries and generals have been coming to the ill-named Demilitarised Zone (DMZ) since the Korean War ended and talking with a mix of chin-jutting determination and studied calm. That is not because any of them trust the North Korean regime, a blend of Stalinist personality cult and blood-soaked feudal dynasty. Americans have sounded determined yet open to negotiations because they are managing what amounts to a six-decade long hostage crisis, during which the North Koreans have assembled tens of thousands of artillery pieces and rocket launchers to hold the southern capital, Seoul, just 55km (34 miles) to the south, in permanent threat.

That effective siege of Seoul continues, and explains why America and its allies have few appealing options, even as Mr Kim sprints ahead with work on intercontinental ballistic missiles that could carry a nuclear warhead to America—a capability that intelligence agencies estimate may be reached within a year.

Until Mr Trump took office, all American presidents have bowed unhappily to that reality, handling the North Koreans as cautiously as police negotiators trying to talk down a murderous hostage-taker. Steadiness, backed by massive firepower, has been the American approach to the North Korean regime, which makes up for its weakness—the country is a wretchedly impoverished communist society of just 25m people—by being uninterested in the welfare of the general population and scornful of any international norms of behaviour.

The DMZ is a mad place, a bad dream of razor-wire fences, sensors and security cameras, vast tank walls to stop an armoured advance, and two million landmines lurking beneath a deceptively bucolic landscape of rolling woodlands. Over the decades North Korea has injected unpredictable violence into this fortified buffer zone many times. KPA troops have killed Americans with axes, provoked fistfights at the truce village and not long ago smuggled anti-personnel mines onto a southern patrol path, blowing the legs off South Korean soldiers. Vast loudspeakers play propaganda songs for up to 18 hours a day, praising the North’s Kim dynasty or urging southern soldiers to defect. The South has built its own loudspeakers, playing cheesy “K-pop” hits. When this blogger—who is one of six reporters travelling around Asia this week aboard Mr Mattis’s plane—accompanied the defence secretary to Observation Point Ouellette, close to the Military Demarcation Line that divides the two Koreas, dueling tunes from the North and South formed a low background burble, competing with the cries of birds of prey that wheel high over no-man’s land.

The American, South Korean and United Nations troops that patrol the southern side of the DMZ have long worked hard to impose as much calm and order on the stand-off as possible. Your blogger first visited the DMZ more than 20 years ago, and as today was sternly lectured by American officers about the need to avoid provocative behaviour. While waiting for Mr Mattis’s statement at the truce village, where the two sides’ sentries stand almost face-to-face, an American reporter was swiftly chided by a lieutenant-colonel for waving his arms around and laughing. “Sir, not in front of the KPA. Try to keep yourself calm and mellow,” growled the colonel. At Ouellette, an American major demurred when asked if he felt the tensions between North Korea and America that make for so many headlines worldwide. “We don’t feel that out here, we try to keep things calm out here,” he said.

American muscle is omnipresent but discreet. Mr Mattis reached the DMZ from downtown Seoul in a fleet of army helicopters, flying fast and low once North Korea was in sight. Our helicopters skimmed hilltops turned autumn golden and red, passing just over a landscape in which the homely—rice fields, schoolboys playing football in a playground, a forklift truck moving boxes—flashed past below in alternation with glimpses of gun emplacements, bunkers and battletanks in rows. We were not permitted to report his visit at the border beforehand.

Returning from the DMZ, our helicopters took just 20 minutes to reach modern, gleaming Seoul, at one point banking hard left to avoid a skyscraper before clattering to land at a city-centre barracks that dates back to the Korean War. Mr Mattis pointed out what is at stake in his remarks at the DMZ, saying the zone separates a “vibrant democracy and thriving economy underpinned by peace-loving members of a free society.” To the north, he said, lies “an oppressive regime that shackles its people,” sacrificing its citizens as it pursues nuclear weapons and the means to deliver them.

Mr Trump’s pugnacious, “America First” rhetoric alarms many members of the public in South Korea and such neighbours as Japan. They wonder if America’s president is willing to sacrifice Seoul by launching a pre-emptive strike on the North if that is what it takes to keep San Francisco or New York safe. Mr Mattis is a loyal cabinet secretary and certainly no dissident. He is as concerned as any conservative hawk with displaying American strength. But in his telling, strength also comes from alliances, whose solidity is sometimes best demonstrated by standing in harm’s way, alongside allies.

Landing in Seoul, the defence secretary greeted a line of soldiers, sailors and airmen. The young men and women squirmed slightly as he urged them to ask him anything that was on their minds. Once government ministers are “done talking”, the burden of keeping countries safe falls on troops, Mr Mattis told them. “We're doing everything we can to solve this diplomatically, everything we can.” He called armed forces a mean of ensuring that diplomats “speak from a position of strength”.

One of the troops asked him about American families living as dependents in Korea. Mr Mattis acknowledged the risks from the North, saying: “Literally right now as you know we’re within range of their fire.” But having American officers and NCOs living in Korea and learning about its society and democracy was a vital way to “build trust” between Koreans and Americans, both of them “proud” peoples.

“You just keep working together and show the world we can do it and we’ll buy time for our diplomats to solve this problem, ok?” Mr Mattis told them. “I gotta go off and act important.” With that he had delivered enough words and was off.

Mr Trump is placing a bet that unpredictability and brinksmanship is a game that America can play, as well as North Korea. Mr Mattis is hewing to an older tradition: one in which America gains from being predictable and leading a rules-based world order. Optimistic senior officials in Asia hope that this is a careful double-act, in which mercurial Mr Trump and steady Mr Mattis pressure and persuade the North Koreans to step back from the brink. Hope that they are right.