Suggestions that the war in Syria is winding down must sound like a sick joke to the people of Ras al-Ain. Their village, in north-western Idlib province, was targeted in an air raid last week. Five residents were killed, including three children, and at least 20 others were injured.

A local man, Hussein al-Sheikh, described to Al Jazeera reporter Farah Najjar how a building collapsed as the children ran for cover: “I was standing near the front door watching the kids play. Suddenly we heard another explosion... It was a difficult scene to watch. I can’t express what I saw.”

The UN estimates that renewed violence in Idlib and adjoining areas has killed dozens of civilians and displaced over 150,000. Aid workers say hospitals, medical facilities and schools have been deliberately targeted with missiles, artillery and barrel bombs.

At first glance, there seems little doubt forces loyal to Bashar al-Assad, Syria’s blood-soaked president, are to blame. They claim to be fighting rebels from a jihadist alliance, Hayat Tahrir al-Sham. But in Syria, as in many other conflict zones around the world, it is not that simple.

Blame must also be laid at the door of Iran, whose Shia militias, backed by Lebanon’s Hezbollah, support the regime. Turkey is at fault, too, for failing to defend a demilitarised zone set up around Idlib last September. And then there is Russia and its merciless warplanes, without whose backing Assad would probably have fallen.

Yet in truth, the net of culpability for eight years of horror must be cast far wider still. The US has largely stood aside from Syria, confining itself to anti-Isis counter-terrorism operations and occasional missile strikes. So too, for the most part, have Britain and Europe.

Russia’s Vladimir Putin forcefully intervened in Syria in 2015. But he did so not to save lives, but to advance Russia’s strategic and security interests in the Middle East – at American expense. UN efforts to negotiate a halt have lacked crucial backing from the great powers.

While none of this is of any comfort to the villagers of Ras al-Ain, the blame for their suffering ultimately lies with a systemic and lethal breakdown in international cooperation over tackling wars and armed conflicts.

In an era when multilateralism has fallen out of fashion, and nationalism coupled with autocratic “strongman” leadership is on the rise, self-interested opportunism has replaced collective responsibility. All but forgotten now are the ideals, based on great power collaboration and a common rulebook, that underpinned the creation of the UN in 1945.

The opposite trend – towards irresponsible great power competition – is everywhere gathering strength, and people are dying daily as a result.

Next time Nigel Farage or Hungary’s Viktor Orban talk about sovereign rights and “taking back control”, it’s worth remembering that ultra-nationalist cant can have murderous international consequences.

When Donald Trump bullies Iran and sells arms to the Saudis, when China’s Xi Jinping incarcerates Muslims, Putin gloats over Crimea, or Brazil’s Jair Bolsonaro defends the razing of rainforests, each is playing to his domestic nationalist base. But the implications for global peace and security are dire.

Libya is a case in point. Eight years after its dictator was toppled to international applause, it risks becoming another Syria. While Egypt, Saudi Arabia and the UAE back a renegade general, Turkey and Qatar support the UN-backed government.

Libyans’ yearning for peace has taken second place to a brutal struggle between regional rivals vying for power, influence and oil.

And Yemen, the world’s worst manmade humanitarian emergency, confirms the trend. Here, too, outside powers have piled in, prioritising geopolitical objectives over saving lives.

The reluctance of states to act collaboratively to halt or prevent wars is matched by a growing propensity to intervene in other people’s battles via surrogates. Direct, state-on-state conflict is increasingly rare. Invasions by multinational coalitions, as in the 1991 Gulf war or Kosovo in 1999, are old hat. But war by proxy is all the rage.

Lower-profile conflicts, in contrast, suffer from international neglect. The absence of energetic external engagement can prove fatal to hopes of peace, as has been the case at different times in South Sudan, the southern Philippines, Myanmar, southern Thailand, Somalia and the Sahel.

Ultra-nationalist “strongman” leaders should know that going it alone rarely works. Recent experience suggests when great powers, eschewing cooperative approaches, attempt unilateral solutions, they usually get nowhere – and often make matters worse.

One example is Israel-Palestine where the US jealously clings to a peace-making monopoly, but has made zero progress. That’s no surprise, given Trump’s chronic pro-Israeli bias. The US is also running private peace talks with the Taliban. Again, success has proved elusive, not least because, amazingly, it has excluded the Afghan government.

Unlike the UN and regional bodies involved in mediation, such as the African Union, national leaders, acting alone, often exhibit selfish motives.

Trump believes he deserves a Nobel peace prize for his summitry with Kim Jong-un. The North Korean dictator’s nuclear weapons build-up is certainly of great international concern. But Trump’s efforts are more vanity project than peace process.

When people talk about the end of multilateralism, it sometimes seems it’s a question of purely academic interest. But as all these unresolved, mostly avoidable wars and conflicts show, it is a matter of life and death. Every day, people are being killed because the world cannot get its act together.