With or without Donald Trump’s help, Kim Jong-un could easily plunge the planet into its third world war inside a century. Of course this one would be vastly more destructive than the Great War, where even the use of aircraft was in its infancy – though sadly not chemical weapons – or World War II, which ended with the first and so far only use of nuclear weapons in war.

To date Donald Trump has played a strong hand. He has installed anti-missile defences against the North inside South Korea. He is doing, more or less, what President Kennedy did in the 1962 Cuban missile crisis, and what President Reagan did in the Cold War in the 1980s: practising brinkmanship, demonstrating strength, displaying resolve. The South Koreans are having elections now, and their new government, after 9 May, may not be as resolute as its predecessor and the Trump administration. Yet while Pyongyang has the capacity to raze Seoul to the ground – even without nuclear weaponry – they may not protest too loudly.

Like Kennedy and Reagan, Trump could prevail. Yet it is not tricky to see how things could spin out of control. Feeling abandoned and exposed, Kim could loose off a few missiles of his own, maybe towards Japan – always a popular target. True to recent form in Afghanistan (the MOAB job) and Syria, President Trump could retaliate with a “surgical” and “proportionate” strike on some North Korean facility. Then what? North Korea sinks a South Korean war ship. There are skirmishes on the ground. Some North Koreans manage to get themselves shot to ribbons. He chucks another missile over the border and it kills American troops. Trump escalates to bombing – conventionally – government buildings and those absurd statues of Kim’s dad and granddad. Kim sees his regime lethally threatened. He now sees no alternative, nothing to lose. A rat cornered, he unleashes his huge conventional forces, supported by Chinese and Russian diplomacy, hoping to get the Americans to back off and leave him in power. Tanks overwhelm the DMZ, American troops are massacred. The US is drawn in. China is faced with gigantic floods of refugees and refuses to permit American troops beyond a certain point near its border. What happens if Japanese, Australian, Nato and other troops fight to defend South Korea? What would Vladimir Putin do?

Donald Trump warns ‘major, major conflict’ with North Korea is ‘absolutely’ possible

The Second Korean War will have begun, with the Third World War not far behind; the long-delayed playing out of the last legacies of the Second World War and the Cold War.

There’s no shortage of ammo. In that corner of the world meet the planet’s biggest and most powerful military forces. The US, pre-eminently, but also Russia, so far content to be more of an observer than a player for now, but another nuclear power. It has long since dropped away from being the Democratic People’s Republic of Korea’s ideological mentor and economic support (dating from when Khrushchev denounced Stalinism, when Mao did not; Pyongyang never looked back). Still, it has a land border with North Korea.

The third nuclear power and the DPRK’s more recent “Communist” friend, China, is more intimately concerned. Taking Donald Trump at his word, it is worried enough to publicly chastise North Korea and push for harsher sanctions. There is South Korea too, rapidly growing its armed forces, and of course North Korea, with a vast army and whatever nuclear and missile technology it has been able to develop. Japan too, though technically limited to “self-defence” has substantial armed forces. It would not take this advanced rich power long to develop nuclear technology if the need arose. In the whole of human history there has never been a bigger powder keg. Nor men so strange playing with a box of matches near to it.

Kim Jong-un is not “crazy”. He, like his dad, is not a nutty despot portrayed so amusingly in Team America or The Interview. He is ruthless though, and paranoid, as we have seen with the elimination of his rivals and critics. If he thinks he has nothing to lose; if America is set on deposing him just the same as Saddam or Gaddafi, and he thinks he will end up being publicly hanged or dismembered anyway, then what is there to stop him taking a few million Koreans and Japanese, plus a few thousand Yankee soldiers, with him?

That is where the danger for President Trump lies. Trump has cleverly made some noises about America not wanting “regime change” in Pyongyang. But what use are words to Kim? The reason Kim wants his nukes and enjoys playing with them so much, like a cunning kid with matches or fireworks, is precisely to freak out the grown-ups all around him, leaders who actually do care about human life and the future of their nations. What Kim sees is a world where America – plus cronies such as South Korea, Japan, the EU and even China or Russia in this case – will get rid of you if you are dumb enough to disarm yourself, or let them interfere with your weapons programmes. So that is why Gaddafi and Saddam are no longer with us; but why Kim and the Iranians are still sitting pretty.

The danger is not so much Trump personally, but what any American president must do if they feel the vital security of the US is at stake, and past policies have failed. And that is to get involved in a gigantic game of “chicken”. I hope that is not trivialising it. Basically, though, what we are talking about here is the sacrifice of South Korea and Japan in order to eliminate some threat of a North Korean missile murdering Americans sometime in the next five years or so. That threat can be assessed as possible, probable or certain, and will shift over time, but seems unlikely to disappear of its own volition, e.g. through massive economic collapse (which is perhaps what the policy of “strategic patience” pursued under Bill Clinton, George W Bush and Barack Obama was secretly all about). It is not a prospect that any president can feel comfortable with however. No president can allow a hostile state to be in a position to hit San Francisco with a nuclear-tipped ICBM if it can stop it from happening.

World news in pictures Show all 50 1 /50 World news in pictures World news in pictures 14 September 2020 Japan's Prime Minister Shinzo Abe, Chief Cabinet Secretary Yoshihide Suga, former Defense Minister Shigeru Ishiba and former Foreign Minister Fumio Kishida celebrate after Suga was elected as new head of the ruling party at the Liberal Democratic Party's leadership election in Tokyo Reuters World news in pictures 13 September 2020 A man stands behind a burning barricade during the fifth straight day of protests against police brutality in Bogota AFP via Getty World news in pictures 12 September 2020 Police officers block and detain protesters during an opposition rally to protest the official presidential election results in Minsk, Belarus. Daily protests calling for the authoritarian president's resignation are now in their second month AP World news in pictures 11 September 2020 Members of 'Omnium Cultural' celebrate the 20th 'Festa per la llibertat' ('Fiesta for the freedom') to mark the Day of Catalonia in Barcelona. Omnion Cultural fights for the independence of Catalonia EPA World news in pictures 10 September 2020 The Moria refugee camp, two days after Greece's biggest migrant camp, was destroyed by fire. Thousands of asylum seekers on the island of Lesbos are now homeless AFP via Getty World news in pictures 9 September 2020 Pope Francis takes off his face mask as he arrives by car to hold a limited public audience at the San Damaso courtyard in The Vatican AFP via Getty World news in pictures 8 September 2020 A home is engulfed in flames during the "Creek Fire" in the Tollhouse area of California AFP via Getty World news in pictures 7 September 2020 A couple take photos along a sea wall of the waves brought by Typhoon Haishen in the eastern port city of Sokcho AFP via Getty World news in pictures 6 September 2020 Novak Djokovic and a tournament official tends to a linesperson who was struck with a ball by Djokovic during his match against Pablo Carreno Busta at the US Open USA Today Sports/Reuters World news in pictures 5 September 2020 Protesters confront police at the Shrine of Remembrance in Melbourne, Australia, during an anti-lockdown rally AFP via Getty World news in pictures 4 September 2020 A woman looks on from a rooftop as rescue workers dig through the rubble of a damaged building in Beirut. A search began for possible survivors after a scanner detected a pulse one month after the mega-blast at the adjacent port AFP via Getty World news in pictures 3 September 2020 A full moon next to the Virgen del Panecillo statue in Quito, Ecuador EPA World news in pictures 2 September 2020 A Palestinian woman reacts as Israeli forces demolish her animal shed near Hebron in the Israeli-occupied West Bank Reuters World news in pictures 1 September 2020 Students protest against presidential elections results in Minsk TUT.BY/AFP via Getty World news in pictures 31 August 2020 The pack rides during the 3rd stage of the Tour de France between Nice and Sisteron AFP via Getty World news in pictures 30 August 2020 Law enforcement officers block a street during a rally of opposition supporters protesting against presidential election results in Minsk, Belarus Reuters World news in pictures 29 August 2020 A woman holding a placard reading "Stop Censorship - Yes to the Freedom of Expression" shouts in a megaphone during a protest against the mandatory wearing of face masks in Paris. Masks, which were already compulsory on public transport, in enclosed public spaces, and outdoors in Paris in certain high-congestion areas around tourist sites, were made mandatory outdoors citywide on August 28 to fight the rising coronavirus infections AFP via Getty World news in pictures 28 August 2020 Japanese Prime Minister Shinzo Abe bows to the national flag at the start of a press conference at the prime minister official residence in Tokyo. Abe announced he will resign over health problems, in a bombshell development that kicks off a leadership contest in the world's third-largest economy AFP via Getty World news in pictures 27 August 2020 Residents take cover behind a tree trunk from rubber bullets fired by South African Police Service (SAPS) in Eldorado Park, near Johannesburg, during a protest by community members after a 16-year old boy was reported dead AFP via Getty World news in pictures 26 August 2020 People scatter rose petals on a statue of Mother Teresa marking her 110th birth anniversary in Ahmedabad AFP via Getty World news in pictures 25 August 2020 An aerial view shows beach-goers standing on salt formations in the Dead Sea near Ein Bokeq, Israel Reuters World news in pictures 24 August 2020 Health workers use a fingertip pulse oximeter and check the body temperature of a fisherwoman inside the Dharavi slum during a door-to-door Covid-19 coronavirus screening in Mumbai AFP via Getty World news in pictures 23 August 2020 People carry an idol of the Hindu god Ganesh, the deity of prosperity, to immerse it off the coast of the Arabian sea during the Ganesh Chaturthi festival in Mumbai, India Reuters World news in pictures 22 August 2020 Firefighters watch as flames from the LNU Lightning Complex fires approach a home in Napa County, California AP World news in pictures 21 August 2020 Members of the Israeli security forces arrest a Palestinian demonstrator during a rally to protest against Israel's plan to annex parts of the occupied West Bank AFP via Getty World news in pictures 20 August 2020 A man pushes his bicycle through a deserted road after prohibitory orders were imposed by district officials for a week to contain the spread of the Covid-19 in Kathmandu AFP via Getty World news in pictures 19 August 2020 A car burns while parked at a residence in Vacaville, California. Dozens of fires are burning out of control throughout Northern California as fire resources are spread thin AFP via Getty World news in pictures 18 August 2020 Students use their mobile phones as flashlights at an anti-government rally at Mahidol University in Nakhon Pathom. Thailand has seen near-daily protests in recent weeks by students demanding the resignation of Prime Minister Prayut Chan-O-Cha AFP via Getty World news in pictures 17 August 2020 Members of the Kayapo tribe block the BR163 highway during a protest outside Novo Progresso in Para state, Brazil. Indigenous protesters blocked a major transamazonian highway to protest against the lack of governmental support during the COVID-19 novel coronavirus pandemic and illegal deforestation in and around their territories AFP via Getty World news in pictures 16 August 2020 Lightning forks over the San Francisco-Oakland Bay Bridge as a storm passes over Oakland AP World news in pictures 15 August 2020 Belarus opposition supporters gather near the Pushkinskaya metro station where Alexander Taraikovsky, a 34-year-old protester died on August 10, during their protest rally in central Minsk AFP via Getty World news in pictures 14 August 2020 AlphaTauri's driver Daniil Kvyat takes part in the second practice session at the Circuit de Catalunya in Montmelo near Barcelona ahead of the Spanish F1 Grand Prix AFP via Getty World news in pictures 13 August 2020 Soldiers of the Brazilian Armed Forces during a disinfection of the Christ The Redeemer statue at the Corcovado mountain prior to the opening of the touristic attraction in Rio AFP via Getty World news in pictures 12 August 2020 Young elephant bulls tussle playfully on World Elephant Day at the Amboseli National Park in Kenya AFP via Getty World news in pictures 11 August 2020 French Prime Minister Jean Castex is helped by a member of staff to put a protective suit on prior to his visit at the CHU hospital in Montpellier AFP via Getty World news in pictures 10 August 2020 Locals harvest their potatoes as Mount Sinabung spews volcanic ash in Karo, North Sumatra province, Indonesia Antara Foto/Reuters World news in pictures 9 August 2020 Doves fly over the Peace Statue at Nagasaki Peace Park during the memorial ceremony held for the 75th anniversary of the atomic bombing EPA World news in pictures 8 August 2020 Anti-government protesters try to remove concrete wall that installed by security forces to prevent protesters reaching the Parliament square, during a protest against the political elites and the government after this week's deadly explosion in Beirut AP World news in pictures 7 August 2020 A protester throws a stone towards Israeli forces in the village of Turmus Aya, north of Ramallah in the occupied West Bank, following a march by Palestinians against the building of Israeli settlements AFP via Getty World news in pictures 6 August 2020 A woman yells as soldiers block a road for French President Emmanuel Macron's visit the Gemmayzeh neighborhood. The area in Beirut suffered extensive damage from the explosion at the seaport AP World news in pictures 5 August 2020 Damage at the site of Tuesday's blast in Beirut's port area, Lebanon Reuters World news in pictures 4 August 2020 A large explosion in the Lebanese capital Beirut. The blast, which rattled entire buildings and broke glass, was felt in several parts of the city AFP via Getty World news in pictures 3 August 2020 A general view shows the new road bridge in Genoa, Italy ahead of its official inauguration, after it was rebuilt following its collapse on August 14, 2018 which killed 43 people Reuters World news in pictures 2 August 2020 Empty stall spaces are seen hours before a citywide curfew is introduced in Melbourne, Australia EPA World news in pictures 1 August 2020 People take part in a demonstration by the initiative "Querdenken-711" with the slogan "the end of the pandemic - the day of freedom" to protest against the current measurements to curb the spread of COVID-19 in Berlin, Germany AFP via Getty World news in pictures 31 July 2020 Pilgrims circumambulating around the Kaaba, the holiest shrine in the Grand mosque in Mecca. Muslim pilgrims converged today on Saudi Arabia's Mount Arafat for the climax of this year's hajj, the smallest in modern times and a sharp contrast to the massive crowds of previous years Saudi Ministry of Media/AFP World news in pictures 30 July 2020 The Mars 2020 Perseverance mission lifts off at the Kennedy Space Centre in Florida. The mission is part of the USA's largest moon to Mars exploration. Nasa will attempt to establish a sustained human presence on and around the moon by 2028 through their Artemis programme EPA World news in pictures 29 July 2020 A woman refreshes herself in a outdoor pool in summer temperatures in Ehingen, Germany dpa via AP World news in pictures 28 July 2020 Malaysia's former prime minister Najib Razak speaks to the media after he was found guilty in his corruption trial in Kuala Lumpur AFP via Getty World news in pictures 27 July 2020 North Korean leader Kim Jong Un poses for a photograph after conferring commemorative pistols to leading commanding officers of the armed forces on the 67th anniversary of the "Day of Victory in the Great Fatherland Liberation War". Which marks the signing of the Korean War armistice KCNA via Reuters

If Trump felt he had no alternative but to make a surgical strike, the consequences are incalculable. Like Kim has in the past, Trump could opt for a low level act of aggression – sinking a North Korean warship, say, or dropping a big conventional bomb on some North Korean facility. It is just impossible to know if Kim would react in kind, escalate matters or just shout a lot. If escalation did begin then when would it go critical? How many lives would be destroyed? How much misery? How much contamination? How much damage to the global economy?

For sure, the costs in human life and treasure would be unprecedented.

We know that, don’t we? I wonder. The UN Security Council reminded the world yesterday that the East Asia region now accounts for about two-fifths of the world’s population and GDP – so it is bigger than the United States or the European Union. Depending on how hairy things get, millions will die, more will be injured and entire economies laid waste. If to think that two consecutive quarters of negative growth constitute an economic recession, terrifying governments, and that a slump is something that lasts for years, consider the prospect of whole nation states and their industrial and financial activities being wiped out for ever. Whereas Germany, Russia and Japan rebuilt after the Second World War, and the two Koreas did so after the horrific wars on their territory that (sort of) ended in 1953, there will be no rebuilding on the decimated toxic nuclear winter that may be left behind in Japan and South Korea this time round. It would make the last financial crisis look tame. Such are the economic relationships between China and the US – the global imbalances where the Chinese keep lending the Americans the cash to live beyond their means – it could wreck America too, financially if not physically. Our world, apart from the odd hermit state such as North Korea, is more interdependent than ever before in more ways. That would also make World War III the most global of conflicts.