The Russo-Ukrainian war is coming down to a race between the weakening political will of western democracies and the deteriorating military means of Vladimir Putin’s dictatorship. But this race will be a marathon, not a sprint. Sustaining that political will requires the kind of farsighted leadership which most democracies are missing. It calls for a recognition that our own countries are also, in some important sense, at war – and a corresponding politics of the long haul.

Is this what you hear when you turn on your television in the United States (where I am now), Germany, Italy, Britain or France? Is this a leading topic in the Conservative party contest to decide Britain’s next prime minister, or the run-up to the Italian election on 25 September, or the campaign for the US midterm elections on 8 November? No, no and no. “We are at war,” I heard someone say recently on the radio; but he was an energy analyst, not a politician.

The fact that Ukrainian forces are preparing for a big counter-offensive to recapture the strategically vital city of Kherson shows what a combination of western arms and Ukrainian courage could achieve. US-supplied High Mobility Artillery Rocket System (Himars) – long–range multiple-launch rocket systems – have enabled the Ukrainians to hit artillery depots, bridges and command posts far behind Russian lines. Russian forces have been redeployed from Donbas to defend against the expected offensive, thus further slowing the Russian advance in the east. Richard Moore, the head of Britain’s Secret Intelligence Service (MI6), observed recently that Russia might be “about to run out of steam” in Ukraine because of shortages of material and adequately trained troops. So Ukraine has a good chance of winning an important battle this autumn; but it’s still a long way from winning the war.

In his campaign to defeat not only Ukraine but also the west, Putin is counting on Russia’s two traditional wartime allies: Field Marshal Time and General Winter. The Russian leader is weaponising energy, reducing gas flows through the Nordstream 1 pipeline so Germany can’t fully replenish its gas storage before the weather turns cold. Then he will have the option of turning off the gas entirely, plunging Germany and other dependent European countries into a desperate winter. High energy prices as a result of the war continue to turbocharge inflation in the west while keeping Putin’s own war chest filled with the billions of euros Germany and others are still paying for Russian gas and oil. Although a few grain ships are now leaving Odesa, his blockade of Ukrainian ports has caused a food price crisis across parts of the Middle East and Africa, resulting in much human misery and potentially in refugee flows and political chaos. Those, too, are Putin’s friends. Better still: the global south seems to blame this at least as much on the west as on Russia.

Putin’s cultural and political analysis of the west leads him to believe that time is on his side. In his view, the west is decadent, weakened by multiculturalism, immigration, the post-nationalism of the EU, LGBTQ+ rights, atheism, pacifism and democracy. No match, therefore, for carnivorous, martial great powers which still cleave to the old trinity of God, family and nation.

There are people in the west who agree with him, subverting western and European unity from within. Just read Viktor Orbán’s scandalous recent speech to an ethnic Hungarian audience in Romania, with its insistence that Hungarians should not become “mixed race”, its sweeping critique of the west’s policy on Ukraine and its conclusion that “Hungary needs to make a new agreement with the Russians”.

Although the party likely to emerge victorious from next month’s Italian elections, the Fratelli d’Italia, is the indirect successor of a neo-fascist party founded in 1946, it does at least support the western position on the war in Ukraine. But the leaders of the Fratelli’s probable coalition partners, the Lega’s Matteo Salvini and Forza Italia’s Silvio Berlusconi have a pro-Putin past and cannot be relied on to stand firm on Ukraine, as the current Italian prime minister, Mario Draghi, has done. In Germany, a plurality of those asked in a recent opinion poll (47%) said Ukraine should give up its eastern territories in return for “peace”. European voices calling on Ukraine to “settle” along those lines will only get louder as the war grinds on. (Former Labour leader Jeremy Corbyn recently joined them, although his intervention won’t affect the strong cross-party consensus in Britain on support for Ukraine.)

Most important are the midterm elections in the US. If Donald Trump announces his presidential candidacy off the back of midterm election successes for his partisans, this could spell big trouble for what has so far been rare bipartisan consensus in the US on large-scale economic and military support for Ukraine. Notoriously reluctant to criticise Putin, Trump has told his supporters that “the Democrats are sending another $40bn to Ukraine, yet America’s parents are struggling to even feed their children”.

What would it take to prove the Russian leader wrong about the intrinsic weakness of western democracies? Rather a lot. The two largest armies in Europe are going to be slogging it out in Ukraine for months and quite probably years to come. Neither side is giving up; neither has a clear path to victory. All the current peace scenarios are unrealistic. When you can’t begin to see how something is going to end, it’s unlikely to end soon.

To sustain Ukraine’s resistance and enable its army to recover lost territory requires weapon supplies on a scale that is large even for America’s military-industrial complex. For example, the US has reportedly already sent one-third of its entire stock of Javelin anti-tank missiles. According to a former deputy governor of the National Bank of Ukraine, the country needs a further $5bn a month in macroeconomic support just to ensure that its economy does not collapse – close to double what it is currently getting. That’s before you even get to the challenge of postwar reconstruction, which may cost as much as $1tn.

If we stay the course, at scale, then Field Marshal Time will be on Ukraine’s side. Putin’s stocks of his most modern weapons and best trained troops have already been depleted. Keep up the pressure and – military experts tell us – he will be reaching back to 40-year-old tanks, and raw recruits. Western sanctions are hitting the hi-tech parts of his economy, needed for resupply. Could he compensate for the loss of skilled troops by a general mobilisation? Will China come to his aid with modern weapons supplies? Can he escalate? These questions have to be asked, of course, but the pressure would be back on him.

In democracies, leaders must justify and explain to voters this kind of large-scale, strategic commitment, otherwise they will not support it in the long run. Putin would then be proved right in his diagnosis of the weakness of democracy. Estonia’s Kaja Kallas is giving an example of such leadership, but then her people know all too much about Russia already. At the moment I don’t see any leader of a major western democracy doing the same, except perhaps for Mario Draghi – and he’s leaving.

• Timothy Garton Ash is a historian, political writer and Guardian columnist