Vladimir Putin, newly elected as Russian president for a fifth term (and being hailed, apparently, by some ultra-nationalist supporters as “imperator” like the tsars before him) has been leading his country’s May 9 Victory Day celebrations in Moscow. As we’ve come to expect, there’s been the usual mix of pomp, nostalgia and military hardware.

It has been said in May each year since Putin sent his war machine across the Ukrainian border in February 2022 that the imperator would want to have a significant battlefield triumph to announce as the country commemorates the Soviet Union’s victory over fascism in the second world war. So far this has proved elusive, thanks to Ukraine’s stubborn defence and the billions of dollars worth of military aid contributed by Kyiv’s western allies.

This time around, largely due to Kyiv’s lack of the latter, Putin has some territorial gains to crow about. Russian forces are pressing Ukrainian defences hard in the east and south of the country, especially in the Donetsk Oblast, where the frontline is creeping, albeit very slowly, towards the strategically important town of Chasiv Yar. Further north, Russian units are edging westwards with the aim of occupying the whole of Luhansk Oblast and moving westwards into eastern Kharkiv Oblast.

But this battlefield progress has reportedly come at a high cost. The UK’s ministry of defence released an intelligence update this week estimating Russian losses through April at 899 soldiers per day killed or wounded, with a total casualty count of more than 465,000 since the conflict began two years ago.

Since Vladimir Putin sent his war machine into Ukraine on February 24 2022, The Conversation has called upon some of the leading experts in international security, geopolitics and military tactics to help our readers understand the big issues. You can also subscribe to our fortnightly recap of expert analysis of the conflict in Ukraine.

It remains unclear, writes Stefan Wolff of the University of Birmingham, the extent to which the US$60 billion (£50 billion) of US military aid is changing this dynamic. Wolff, an expert in international security who has been a regular contributor to our coverage of the war since it started, says that despite the US having positioned key supplies close enough to Ukraine’s troops to be delivered in some cases within a few hours, there is........

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