The war for Ukraine gets darker and more terrifying, and now a new front has opened up many miles away – in a US Republican party whose biggest players are itching to abandon Ukraine to its fate. Proof of the conflict’s deepening horror came this week, with the destruction on Tuesday of the Kakhovka dam in Russian-controlled Ukraine, releasing a body of water so massive it’s best imagined not as a reservoir but as a great lake. The result has been the flooding of a vast swath of terrain, forcing thousands to abandon their homes and flee for their lives. But the menaces unleashed by this act go further than the immediate and devastating effect on the people who live close by. For one thing, this calamity has hit a region of rich and fertile farmland, the same soil that long made Ukraine a breadbasket for the world: the fifth-largest exporter of wheat on the planet, the food source on which much of Africa and the Middle East has relied. Now there are warnings that the fields of southern Ukraine could “turn into deserts” by next year, because the water held back by the dam and needed to irrigate those fields is draining away. That will have an impact on food supplies and food prices, with an effect in turn on inflation and the global economy. Not that the international impact can be measured in dollars and cents alone. Volodymyr Zelenskiy has warned that contaminated floodwaters now carry with them sewage, oil, chemicals and even anthrax from animal burial sites. That toxic material will, said the Ukrainian president, poison rivers and, before long, the water basin of the Black Sea. “So it’s not happening somewhere else. It is all interrelated in the world.” Meanwhile, the Red Cross has sounded an alarm of its own: the bursting of the dam does grievous damage to its ongoing effort to locate and clear landmines in the area. “We knew where the hazards were,” the organisation lamented. “Now we don’t know. All we know is that they are somewhere downstream.” Dislodged by the racing waters, those devices are now floating mines. And that’s before you reckon with the Zaporizhzhia nuclear power plant, the biggest in Europe, which relies on water from the now-draining reservoir for the essential process of cooling. Small wonder that Zelenskiy speaks of “an environmental bomb of mass destruction,” while others now mention Kakhovka in the same breath as Chornobyl. Except few believe this was an accident. Naturally, Moscow insists that this was not a Russian act: it says the Ukrainians did this to themselves. Still, and even though investigations are ongoing, it’s worth heeding the advice of the specialist in Ukrainian history Timothy Snyder, and remembering the fundamentals of detective work. “Russia had the means,” Snyder notes, in that Russia was in control of the relevant part of the dam when it appeared to explode. Russia had the motive, in that it fears a Ukrainian counteroffensive aimed at taking back territory – and flooded ground is ground over which tanks cannot advance. And there is the pattern of behaviour, the record of past crimes. Russia has scarcely restrained itself from targeting Ukraine’s civil infrastructure over the last 15 months: Kakhovka would just be the latest and most wanton example. Indeed, the destruction of dams to trigger mass flooding is no more than Russia’s ultra-nationalist talking heads and TV pundit class have been demanding for a while. This week one such voice suggested Moscow give the Kyiv dam the Kakhovka treatment and that it “raze the city to the ground”. As if weighing up the moral implications, he asked, “Why should we be holier than the pope?” The official denials should not be taken too seriously, given the Kremlin’s history of disinformation and outright lies. Better to judge Russia by its deeds than its words. So what did Russia do to help those made desperate by the floods? The answer was swift and it came from Russian artillery units, seemingly firing on Ukrainian rescue workers and evacuees as they tried to flee to safety. It’s a strategy familiar from Moscow’s war in Syria: pile pain upon pain, misery upon misery. Supporters of Ukraine say that this is a sign of Russian weakness, that it is resorting to barbaric methods because it knows that, in key respects, Ukraine has the upper hand – not least because it enjoys the support of a united west. That is true, for now. But there is a threat from within the alliance’s most powerful member. Freshly indicted though he is, Donald Trump remains the frontrunner for the Republican nomination for president. And Trump is a well-documented friend of Vladimir Putin and a sceptic on the merits of continued US support for Kyiv. When asked on CNN last month, the former president couldn’t say who he wants to prevail in the contest between Russia and Ukraine, between invader and invaded. Nor would he commit to supplying aid to Kyiv: “We don’t have ammunition for ourselves, we’re giving away so much.” Asked about war crimes charges against Putin – centred on the alleged mass abduction of Ukrainian children and their transfer across the border to be “re-educated” as Russians – Trump again refused to condemn the “smart guy” in the Kremlin. Because Trump has remade the Republican party in his own image, this is not a danger confined to him alone. His nearest current rival, the Florida governor, Ron DeSantis, echoed Moscow talking points in March when he referred to the war as a “territorial dispute”, a remark he later sought to undo. But the window into his thinking had been opened. Most Republicans in Congress still back Ukraine, but the right of the party has moved into a different place, one illuminated by Tucker Carlson’s debut Twitter show this week, his first since his firing by Fox News. There he described Zelenskiy, who is Jewish, as “sweaty and rat-like … a persecutor of Christians … shifty, dead-eyed”, suggesting without evidence, and in a perfect echo of Moscow, that the hand of Kyiv lay behind the destruction of the Kakhovka dam. We already knew that much is at stake in the November 2024 presidential election, not least the life expectancy of US democracy. But there is something else, too. Ukraine is engaged in a profound battle for its own survival as an independent nation, and for larger principles essential to the whole world: that freedom must prevail, and that aggression must not. Ukraine cannot win that fight alone. It cannot win only with the backing of its European neighbours, which, though necessary, is not sufficient. It requires the United States, its muscle and its money. The plight of Kherson and the indictment in Miami are linked: the world desperately needs the defeat of Donald Trump. Jonathan Freedland is a Guardian columnist