This time last year, Volodymyr Zelensky was touring western capitals, calling for weapons and money to launch a decisive summer offensive. Nato eventually provided Leopard and Challenger tanks, Bradley infantry fighting vehicles, M777 howitzers, Himars rocket artillery and Patriot air defences – but too little, too late. The much-vaunted offensive went nowhere, despite a mutiny by the Wagner Group and widespread disarray in the Russian army. Instead, Soledar, Bakhmut and Avdiivka were seized. Today, Russian missile assaults are intensifying, not receding. In March, Russia hit Ukraine with 264 missiles and 515 drones. A relentless bombardment of Kharkiv is making Ukraine’s second city uninhabitable.

In response, Kyiv’s most successful strategy to date has been its ingenious use of Ukrainian-made long-range drones to strike oil refineries, gas liquefaction plants, military airfields, arms factories and petrol storage facilities deep inside Russia. These daily attacks are growing bolder and more sophisticated, from a musical drone that blared German music – Apocalypse Now-style – as it honed in on its target, to a converted pilot-less Cessna plane backed with explosives that struck a Shahed drone factory in Tatarstan, 750 miles from Ukraine.

The Washington-based Institute for the Study of War has said that the attacks represent ‘a significant inflection in Ukraine’s demonstrated capability to conduct long-range strikes far into the Russian rear’. And the strategy is hurting Russia: 15 of its 30 oil refineries have been struck since January, knocking out 10 to 14 per cent of the refinery capacity, driving prices up at the pumps and prompting the Kremlin to impose restrictions on gasoline exports from March to September. Moscow and other major battlefield targets are protected by air defence systems, but the country can’t possibly defend every installation in its vast territory; its size is its vulnerability.

But, dangerously for Ukraine, the success and frequency of its assaults inside Russia have drawn criticism from allies. Joe Biden’s administration has distanced itself from Kyiv over the attacks. ‘It has been our policy from day one to do everything possible to help Ukraine defend itself against Russian aggression,’ Antony Blinken, the US Secretary of State, said last week. ‘At the same time we have neither supported or enabled strikes by Ukraine outside its territory.’

Blinken hasn’t condemned Ukraine; the US could likely put a stop to strikes if it really wanted to. His words, however, signal that the White House is alarmed – and wants to communicate to the Kremlin that Kyiv, not Washington, is the driving force behind the deep strikes. The German government last month announced it wouldn’t send Taurus cruise missiles (which have an effective range of more than 300 miles) to Ukraine for fear they would be used to hit Russian targets.

Of all Ukraine’s allies, only Emmanuel Macron has upped the ante, refusing to rule out deploying French troops and reminding Vladimir Putin that Nato, too, has nukes. France’s defence minister said this week that it’s not in the West’s ‘interests’ to continue talking to the Kremlin after a rare and frustrating phone call with his Russian counterpart. During the call, Sergei Shoigu replied to a French offer of security co-operation on Islamist terror with a slew of conspiracy theories about the recent Crocus City Hall attack that left at least 144 Muscovites dead. David Cameron, though less forthright than Macron, travelled to America this week in a well-meaning but probably doomed attempt to convince Donald Trump to reverse his opposition to Ukrainian aid.

One reason for US hesitancy goes back to the start of the conflict. When General Mark Milley, Chairman of the Joint Chiefs of Staff, first briefed Biden’s security team about a possible Russian invasion in October 2021, he set out America’s key priorities. Number one was how to support and defend Ukraine ‘without getting the US into a kinetic war with Russia’. Several red lines which the Kremlin claimed would be regarded as an act of war against Russia (the delivery of MiG fighters, main battle tanks and ATACMS rocket artillery to Ukraine) were ignored. However, there remains one line the US is unwilling to cross – directly supporting Ukrainian attacks on Russian soil.

According to Michael McCaul, Republican head of the House Foreign Affairs Committee and (unlike many of his party) a supporter of military aid to Ukraine, several senior figures in Biden’s administration are more frightened about a nuclear escalation than they were at the start of the war. ‘It’s not Blinken’ who is scared, McCaul said last week. ‘I was with him right after the invasion – he was all in for the MiGs going in. It’s not him. In my judgment, it’s [National Security Adviser] Jake Sullivan and the White House. Jake is overly cautious. He’s very timid. And he’s bought into this notion that if we give [Ukraine] too much, then Russia’s going to use a tactical nuke on us.’

There’s a selfish political logic in this caution. In what promises to be a turbulent election year, and with military aid to Ukraine a partisan issue in Congress, the last thing Biden needs is a battle between Russia and Nato. If Ukrainian strikes seriously damage Russia’s oil and gas export infrastructure, it’ll cause higher global energy prices – which will harm Biden politically and pour money into the coffers of Iran and Russia. But domestic US political considerations aside, there are also signs that the mood in the Kremlin is becoming more febrile and irrational – and therefore more dangerous.

In the wake of the Crocus City attack, senior Kremlin courtiers and Putin himself have, for the first time, begun speaking directly of western involvement in anti-Russian terror and accused Washington of waging a war to annihilate Russia. Dmitry Medvedev, the former president and current security council deputy chairman, claimed the attackers’ ‘real employers are the Ukrainian Banderovites [ultranationalists], your hatchet men. And the accomplices in this murder are all of you, Biden, Macron, Sunak, Scholz and other minions’. The battered terror suspects, meanwhile, confessed on TV to a plan to head to Kyiv after the attack.

Sullivan’s growing nervousness isn’t irrational; and it’s shared by other western intelligence services. ‘I don’t think we’re talking about [the Kremlin] going full Dr Strangelove,’ says a senior UK intelligence officer who briefs Rishi Sunak regularly. ‘But we’re seeing an increasing detachment from reality that’s very concerning.’

The combination of partisan deadlock in Washington and a wider western fear of escalation leaves Ukraine in a desperate place. Verbally, Nato claims to remain committed to supporting Kyiv. But with European supplies of artillery shells and missile-defence ammunition running seriously low, and the lion’s share of aid from the US stalled, such support sounds increasingly hollow.

‘One [scenario] is that Nato allies are able to mobilise more support, and that Ukraine is able to regain more territory,’ Nato Secretary-General Jens Stoltenberg said recently. ‘The other scenario is that we are not able to do so, and there is a real threat that Russia will capture even more territories and we will be in an even more dangerous position.’ It’s clear which outcome Stoltenberg thinks is more likely. ‘At the end of the day,’ he added, ‘it has to be Ukraine that decides what kind of compromises they’re willing to do, we need to enable them to be in a position where they actually achieve an acceptable result around the negotiating table.’

Nato military analysts have been briefing that they don’t believe Russia has the manpower or resources to mount a major land offensive. But the same goes for Ukraine. Zelensky recently lowered the country’s minimum draft age from 27 to 25. Yet General Oleksandr Syrsky, Ukraine’s new military chief, said his predecessor’s idea of 500,000 new soldiers isn’t viable. Legislation to widen the parameters of who can be conscripted has been cut to pieces by lawmakers. Videos on Ukrainian social media show brutal press-gang style seizures of young men off the streets that sometimes end in the conscripts being rescued by passers-by. Mobilisation is becoming the focal point of political discontent.

There’s also a question over what weapons Ukraine needs. Zelensky’s 2023 shopping list included F-16 fighters. But with the main vector of the war shifting to long-range missile and drone strikes it’s not clear how effective the dozen F-16s will be when they become operational this summer.

Putin’s plan appears to be to pummel Ukraine’s cities mercilessly and then slog forward on the ground. Cruise missiles and hypersonic Kinzhal ballistic missiles have been taking roundabout routes to their targets, avoiding defensive batteries. But Putin’s ministers have also been shown touring factories producing new, massive glide bombs, the FAB-1500 and the FAB-3000 (the numbers indicating kilos) that guide themselves to targets using rudimentary wings and onboard geolocation computers. Between February 2022 and January this year, Russia damaged or destroyed some $9 billion of Ukrainian energy infrastructure, and the scale of the damage is increasing. Kharkiv’s electricity grid has been demolished. If his forces cannot take the city, Putin seems determined to destroy it as he did Mariupol, Severodonetsk and Bakhmut, making a mockery of his earlier claims that he sees the Russian-speaking population of Kharkiv as fellow countrymen.

Ukraine’s long-range drone strikes are harming the Russian war machine. In time, it’s likely they will succeed in destroying the bridge linking Krasnodar territory to the annexed Crimean peninsula. But there’s no sign yet that Kyiv is anywhere close to destroying Moscow’s offensive capabilities.

Russian tactics of heavy bombing alternated with human-wave attacks are slowly delivering territory to Putin, even if a major offensive is off the cards. That means Russia has very little incentive to freeze the conflict. The Russian economy, far from being crippled by western sanctions, is set to grow, thanks to massive state military spending and sales of oil and gas to China and India. ‘China is propping up the Russian war economy, delivering key parts to the defence industry,’ said Stoltenberg. ‘In return Moscow is mortgaging its future to Beijing.’

When talks eventually begin, Russia is likely to insist on the same arrangements it demanded in Istanbul in April 2022: a neutral Ukraine, plus the already occupied territories and whatever they succeed in occupying after that. Trump has reportedly told top associates he plans to end the war by ‘pressuring Ukraine to give up some territory’.

Putin’s goal is to manoeuvre for maximum military advantage in order to bring the war to a close on his own terms, some time after the US election. If he succeeds, it will be because Washington didn’t have the resolve or willingness to face him down.