The tank commander rubbed his hands. After hours of heavy fighting, the enemy had been forced to retreat. The way through to the next city was now clear. "Forward!" he ordered. The powerful engines roared into life - but the tank did not move. Peering from the turret, he made a sickening discovery: he was stuck in the mud.

This is the fate that befell many German armoured vehicles during the Nazi invasion of Russia in 1941. Ukrainians now hope that the same thing will happen to Russian tanks as they head for the east.

President Zelensky has warned that, following Russia's failure to capture Kyiv, the invaders are sending tens of thousands of extra troops to fight in the Donbas region. Tanks will play a vital role: the Russian army operates in Battalion Tactical Groups (BTGs) formed around them.

According to Professor Phillips O'Brien of St Andrews University, "BTGs are a way of creating a fighting unit with lots of punch. They're designed to attack quickly with lots of firepower."

The tanks, however, have very few troops to protect them if they come under attack. "That makes the Russian army like a boxer who has a great right hook and a glass jawA weakness making someone vulnerable to a knockout punch.."

Russia had an estimated 2,700 tanks at the start of the war. So far, it is believed to have lost between 460 and 680 of them.

Half of these have been destroyed by drones and anti-tank missiles. The US and UK have supplied around 8,000 Javelin and NLAWShort for Next Generation Light Anti-tank Weapon. missiles, which target the top of a tank where the armour is weakest.

But many other tanks have been lost through Russian incompetence - including bad driving. "Some have been driven off bridges," says Nick Reynolds, an expert from the Royal United Services InstituteAn organisation founded by the Duke of Wellington in 1831 to study military matters.. "Others have been driven into ditches so that the tracks have come off."

Others have simply run out of fuel, been abandoned by fleeing soldiers - or got stuck in the mud. According to Britain's armed forces minister James Heappey, President Putin got the timing of his invasion badly wrong:

"You can conduct military operations in Ukraine either in the dead of winter when the ground is frozen solid or in the summer when the ground is dry and hard. The mud of Ukraine in the springtime brought the Nazis to a standstill in Operation Barbarossa, and Putin's desire to have a 9 May victory paradeAn annual event commemorating the victory over Germany in 1945. Putin is thought to be hoping to celebrate victory over Ukraine at the same time. through Moscow is just characteristic of the hubrisArrogance. In Greek tragedy, hubris is the key flaw that brings disaster to humans. and utter disregard for loss of Russian life that he's shown so far."

As the Russians advance towards Donbas, he adds, "They will be forced to remain on roads, because the mud does not allow for armoured manoeuvre across the country. And what we'll see therefore is highly canalisedForced into a narrow channel. Russian columns that, as we saw north of Kyiv, present the Ukrainians with pretty easy pickings."

But according to a Russian expert, Vasily Kashin, 9 May is irrelevant to Putin's thinking. "This is a hard war, the largest in Europe since 1945. No one is going to time anything to fit with a public holiday."

Yes: He believes that he should have a place in history like Russia's World War Two leader, Stalin. His arrogance makes him reluctant to take advice, which is why his forces have done so badly in Ukraine.

No: Even if the war in Ukraine is a complete disaster for Russia, Putin's position is secure. He has eliminated his rivals with such ruthlessness that nobody will dare to challenge him.   

Or... Putin is guilty not of hubris but of making a simple mistake. He underestimated the bravery and determination of the Ukrainians, but many people in the West have been surprised by them too.