When the hastily confected Fifa world peace prize was bestowed on Donald Trump last week, the ceasefire in the Thai-Cambodian border dispute was among the achievements cited. Mr Trump also boasted of having ended war in the Democratic Republic of the Congo. He brags of having brought eight conflicts to a close and has just had the US Institute of Peace renamed in his honour.

Yet the truce between Thailand and Cambodia has already fallen apart. Half a million residents along the border have fled renewed fighting and civilians are among at least 27 people killed. Meanwhile, in the east of the Democratic Republic of the Congo, at least 200,000 people have fled the advance of Rwanda-backed M23 rebels – days after a peace deal was signed in Washington.

On Friday, Mr Trump declared that the two sides had agreed to put down arms again. But they disagreed and fighting continued over the weekend. Bangkok reluctantly agreed to the July deal because the US wielded tariffs as leverage. Phnom Penh, in the weaker position, was happier for it to intercede. Thailand then accused Cambodia – with good evidence – of laying new landmines in border areas, injuring several Thai soldiers. The conflict reignited in early December, with each side blaming the other.

The territorial dispute between Thailand and Cambodia is more than a century old and centred on disagreements over colonial-era maps. The two countries have clashed before over an ancient temple and seen unrest over who can claim other aspects of heritage. Thailand has also attacked the proliferation of criminal online scam centres in Cambodia. What gives the disagreement such potency, however, is that in both countries nationalist feeling has been weaponised for domestic purposes. In Cambodia, where the longstanding ruler Hun Sen has given way to his son Hun Manet in a dynastic dictatorship, whipping up anger against its neighbour helps to legitimise a regime that has little to offer its people.

In Thailand, the long-running clash between the powerful military and royalist elites and the politician Thaksin Shinawatra, his family and proxies has been key. In August, a court dismissed his daughter Paetongtarn Shinawatra as prime minister for failing to protect the country’s interests, after a recording of her discussing the border dispute with Hun Sen was leaked. It captured her addressing him as “uncle”, promising to “take care of it”, and denigrating a key military commander – prompting a storm of outrage. It played to political opponents’ claims that the Shinawatra family were happy to sell the country’s interests for personal benefit.

The caretaker prime minister appointed in her stead has courted popularity by giving the military free rein in its stated aim of crippling the Cambodian army. Ahead of promised elections, the clashes are distracting from governmental woes – including a poor response to deadly floods – as well as positioning the army as national champions.

Mr Trump, who predicted that he could settle the renewed conflict “pretty quickly”, wants instant wins and photo opportunities. Leaders who fear alienating him may provide handshakes and promises when pushed to it. But while pressure from powerful external players can help to push the parties in regional disputes to the negotiating table, there is a big difference between quick fixes and lasting peace – as the airstrikes and rocket attacks along the Thai-Cambodian border demonstrate.

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