Russia's forces are exhausted and possibly demoralised after sustaining three months of intensive attacks, including long-range strikes that are targeting their supply lines. If Ukraine can break through the remaining Russian defences and reach as far as the town of Tokmak then this would bring Russia's rail and road supply routes for Crimea within range of its artillery. If they can do that, then this counter offensive can be judged a qualified success. It may not end the war, which is likely to drag on well into 2024 and perhaps longer - but it would seriously undermine Moscow's war effort and put Ukraine in a strong position for when peace talks eventually begin. But for Kyiv, the clock is ticking. The rainy season will arrive within weeks, turning the roads to mud and hindering further advances. Beyond that lies the uncertainty of the US presidential elections, where a Republican victory could see US military support for Ukraine dramatically slashed.
President Putin knows he needs to tough it out until then. The Ukrainians know they have got to make this counter-offensive succeed.