Vladimir Putin's war in Ukraine went wrong from the very first day but the paradox is that two months later it is entering its most dangerous phase: an unstable and violent stalemate.

NATO and the Pentagon variously estimate Russia has suffered between 7,000 and 15,000 war deaths and up to 30,000 serious injuries. These losses have not just been among the poorly trained new recruits and conscripts but have extended to the elite forces spearheading the entire assault.

One of these, the 331st Guards Parachute Regiment lost at least 40 of its soldiers in the first three weeks, including its commanding officer, Colonel Sergei Sukharev. By six weeks, its losses were reported to be more than double that, at around a hundred. Given that at least twice that number would have been seriously injured, more than a third of the entire regiment is likely to have been wiped out.

This week, the Pentagon assessed that Putin's army has now lost 25% of the entire combat power - troops, weapons and military equipment - deployed to Ukraine. As two-thirds of the entire Russian Army is involved and we are only eight weeks into the war, the size of Putin's disaster is clear, if not to him.

Russia's war aims have now been reduced to taking as much control of Donbas as possible before declaring victory, the assumption perhaps being that sheer force of military numbers will eventually wear down Zelenskyi's government. What this overlooks, though, is that Putin is now also fighting a very real proxy war against NATO. Losing would be a disaster for either side, hence the stalemate.

To put NATO's involvement in perspective, it began by providing short-range defensive weapons such as anti-armour and anti-aircraft missiles and light armaments, as well as medical supplies and a wide array of supporting matériel. That is both increasing and changing as the war moves to Donbas and the need for different weapons emerges.

Up to ten large military transports a day are currently being flown into half a dozen staging bases convenient for Ukraine, mostly in Poland and Romania. From there, hundreds of trucks take them across the border, where they are then fanned out via numerous routes across Ukraine.

Some of the items now being sent are substantial, such as long-range howitzer artillery, which will be used to try and destroy the Russian artillery that has been used to devastating effect against civilian targets. Earlier this week, the first of the 18 155mm US howitzers arrived in Europe, along with the first shipment of the 40,000 rounds of ammunition. With a range of up to 25 kilometres and a firing rate of four rounds a minute, these are formidable in the counter-battery role, especially when supported by precise targeting data from the US.

The howitzers have only some similarities with their Russian equivalents, so a core team of 50 experienced Ukrainian soldiers is currently getting a crash course on the weapons in neighbouring countries. The soldiers will then return to Ukraine to teach their own people. This is just the start of a major programme; on 21 April it was announced that a further 72 howitzers with 72 tractors will follow, along with another 144,000 rounds of ammunition. This takes the situation about as close to a direct Russia-NATO war as you can get.

There are many other connections that rarely see the light of day, the sharing of intelligence being one. There is an underlying assumption in the Pentagon, the CIA and all the other parts of the US war machine that Russia is one of two likely candidates - the other being China - to be a direct opponent to the US in a future war. The war in Ukraine is therefore seen as a remarkable opportunity to practice fighting Russia. It is too good a chance to miss.

There are inevitably questions on how far the US can go, and how state-of-the-art its weapons can be, before the situation also becomes a useful learning opportunity for Russia. Given the huge US reconnaissance and intelligence-gathering capability, though, it is a confident assumption that Ukraine is getting 24/7 data on the entire Russian war machine, no doubt one of the factors that led to the sinking of the Moskva, Russia's flagship warship, a fortnight ago.

That incident alone was a disaster for the Kremlin. The entire Russian Navy has just six capital warships - an aircraft carrier, two battlecruisers and three cruisers. Of these, one carrier has been plagued with problems for years and one battlecruiser remains unfinished, having been under construction for more than 20 years. This leaves Russia with just four ships, one of which has now been sunk.

More generally, given Russia's heavy losses and need to amalgamate and re-train its units, it is frankly unlikely that its performance in eastern Ukraine will be any better than in the north, including around Kyiv. There may be talk of bringing in mercenaries such as the Wagner Group and Syrian irregulars, but the numbers are small and integrating them effectively into existing units will take far more time than the Kremlin has.

What this all adds up to is a long, slow war of attrition, until one side is prepared to give way. Despite the many thousands of lives lost and the $60bn of damage suffered by Ukraine, the Zelenskyi government is still prepared to compromise, at least to an extent. Putin is not, but the two factors that could change his stance are the same as they have been for many weeks. One is if China decides Putin's war is bad for its own global image, at which point Beijing may decide to pull the plug as the only state with that kind of power over Moscow.

The other, not to be underestimated, is the impact of casualties on Putin's domestic support. Even with the Kremlin's wall-to-wall media control, that upwards of 40,000 young soldiers have been killed or seriously injured simply belies the notion that the war is going well. With Russian troops in Donbas having to take on experienced Ukrainian troops in well-prepared defensive positions, equipped with up-to-date weapons from NATO, the number of Russian casualties will most likely increase by 5,000 or more each week for as long as the war continues.

At some stage, Putin will end up with a choice between either seeking a negotiated settlement or opting to threaten escalation to far more destructive weapons. Diplomatic skills and a willingness to compromise by Ukraine and its NATO allies will then become critically important. That point could come in the next couple of months, but it could still be a year or more away.

From openDemocracy