It has been an unusually wet but mild autumn in Ukraine — but that is set to change, with temperatures forecast to drop significantly in Kherson at the weekend to well below freezing.
That will mark the start of the winter war and could be a defining moment in combat operations in the country.
The side that comes out on top by spring may well dictate the course of the war and whatever final settlement brings peace.
Experts believe that current conditions favour the Ukrainians but Russia’s resilience and ability to adapt cannot be dismissed — nor can their long history of successful winter warfare.
When Napoleon invaded in June 1812, it was “General Winter” that devastated the 450,000-strong French army as it retreated from Moscow, with only 40,000 limping into Paris by December.
Adolf Hitler’s troops suffered the same fate in World War Two: the Soviets conducted several winter offensives, including one in which they surrounded the Germans in Stalingrad precisely 80 years ago.
There is a question over whether the current Russian army will retain the willpower or ability to continue fighting. Nothing breaks morale quicker on the front line than frozen extremities, cold rations and the realisation that warmth is permanently unattainable.
“In harsh winter weather, leadership and morale, team cohesion and believing you're fighting for a just cause becomes ever more important,” said former British Army Brigadier Ben Barry. “This is a truth that's universally ignored.”
Morale is only one component of winter war — functioning and effective equipment is also key to good spirits and fighting capability.
When the Wehrmacht reached the outskirts of Moscow in late 1941, their commanders realised too late that they had no winter clothing and German households belatedly handed over their personal furs to the front line.
Canada, a country of extreme freezing temperatures, is sending Ukraine 500,000 sets of cold-weather clothing, from winter parkas to trousers, boots and gloves. Britain is also providing 25,000 sets of extreme cold-weather clothing as well as 12,000 sleeping kits and 150 heated tents.
By comparison, Russian reservists are said to be arriving without sleeping bags and with reportedly low-grade equipment. While they will know about extreme cold conditions from home, it will be different being out in the open on the front line.
The Ukrainian military has realised that those who are better prepared will have the advantage.
“When a soldier is in warm clothes, he will fight in the cold; when the ground is dry and hard, he will feel comfortable and then there will be a tendency to intensify hostilities,” said Ukrainian reservist Col Oleh Zhdanov.
Sam Cranny-Evans of the Rusi think tank said: “The temperature is dropping rapidly so it's a big question over whether both sides are actually ready for winter coming as it will be cold, wet and freezing which can certainly exacerbate the fighting spirit.”
Already combat conditions are changing, with autumnal storms stripping trees of leaves that offer cover, particularly from the many surveillance drones.
Less leaf cover makes it harder to spot the enemy, allowing for fewer ambushes and battles conducted at a greater distance with tank and artillery duels.
The storms have also brought on rivers of mud, making the evacuation of wounded a real challenge. Britain’s defence ministry warned in a recent report that medics were struggling to evacuate soldiers in the “golden hour”, the time frame given to get them to the operating theatre with the highest chance of saving their lives.
“We can expect more fatalities as a consequence of injuries on the battlefield,” one defence source said.
The wet, damp conditions are also leading to spikes in flu and tetanus cases. Soldiers are also injuring themselves by slipping in the mud and on one occasion this month, a Ukrainian ambulance slid down a verge almost into a river.
The coming plunge in temperatures will freeze the mud but will also prove a test for both sides’ equipment.
“Winter is going to have an effect on performance particularly on sensors and with the longer nights,” said Brig Barry, who served two winters on operations in Bosnia.
“The simple, cheap commercial drones just have optical cameras and no low light capability. It's only the expensive military-grade drones that have thermal cameras that can detect armoured vehicles under cover but they will still have problems in freezing fog.”
The freeze will also affect drone use with navigation systems liable to ice over.
While the snow will make it easier to hide landmines, it will also require more fuel for generators. Logistics troops will also have to get used to driving and navigating in the dark with the tree cover gone and shorter days.
With cold air being denser than warm, riflemen will have to adjust to bullets travelling slower.
The concrete-hard ground will also prove deadly, with artillery shrapnel otherwise mitigated by softer ground.
Both sides have Soviet-era equipment that is well adapted to harsh winters but this will prove a test for Ukraine’s modern Nato vehicles.
“The Soviet-era vehicles are specifically designed for cold and soldiers will know how to get them started and keep them running with antifreeze and specific motor oil,” said Mr Cranny-Evans.
“It’s a question of which side trains and adapts best for winter maintenance. The Soviet armour also has wider tracks which helps in mud and snow.”
Both sides might decide to build up their strength before the freeze fully arrives. Russia will want to hold its ground while it trains up more soldiers and, more importantly, rebuilds its vastly depleted ammunition stockpile.
There could well be a reduction in the fighting during the winter, but come December or January, the Ukrainians, with their better winter protection and momentum from taking the city of Kherson, may decide to press on with recapturing more territory.
“Both sides doctrinally can fight in the winter so it depends on the choices they make,” a western official told The National.
“Is it their intent to rebuild and reconstitute forces and munitions ready for a spring offensive or will they continue on the offensive during winter as new personnel and munitions arrive? We shall see.”
He warned that the Russians were “in a better state” than the cold of their February invasion “but I don't think they have closed the gap on their winter gear to people on the front so we'll see how winter starts to affect morale”.
That morale factor may soon become apparent.
The cold might slow the tempo of Ukraine’s counter-offensive, giving Russia’s generals the chance to recuperate — which may well have been their calculation in withdrawing from Kherson.
But they also have a 1,100km front line to defend as well as troops to train, equip and supply.
If Russia fails to adequately support its troops, the relentless cold could make an irreparable dent in their willingness to continue fighting for a questionable cause.
“Leadership and belief in your cause and morale is key in those conditions and it seems to me that the Ukrainians have an advantage compared with Russia in that department,” said Brig Barry.
Mykola Bielieskov, a Ukrainian analyst, argued that “sustaining morale” was the most important factor in winter on both sides.
“There’s a real possibility that Russian forces in the field might cross a point of no return if they’re not properly sustained,” he said.