The looming battle against Russian forces in the east will be similar to combat during World War II, Ukraine's foreign minister has warned as he pleaded with Nato allies to provide more weapons in "days, not weeks".
As the Russian army prepared to launch a major offensive in the Donbas region, Dmytro Kuleba warned that Moscow would commit more atrocities against civilians unless Kyiv's troops were supported with Western artillery, jets and air defence systems.
"Either you help us now – and I'm speaking about days, not weeks – or your help will come too late and many people will die, many civilians will lose their homes, many villages will be destroyed, exactly because this help came too late," he said.
Kuleba was referring to war crimes committed by Russian forces before their withdrawal from around Kyiv, including the torture and execution of hundreds of civilians.
He said: "The battle for Donbas will remind you of the Second World War, with large operations manoeuvres, the involvement of thousands of tanks, armoured vehicles, planes, artillery. Russia has its plan, we have ours – and the outcome of this battle will be decided on the battlefield."
Kuleba said Ukraine had already outlined its requests for heavier weaponry, such as air defence systems, artillery, armoured vehicles and jets, and that the key factor was delivering them before the Donbas offensive started.
"I have no doubts that Ukraine will have weapons necessary to fight. The question is the timeline," he said. "This discussion is not about the list of weapons. The discussion is about the timeline."
Turkish mediators warned that Russian war crimes in towns such as Bucha risked derailing peace talks.
"The developments on the ground, pictures coming out of Bucha and now a few other places, make it of course more difficult for the negotiations to continue as before," Ibrahim Kalin, an adviser to the Turkish presidency, told the Financial Times.
Sergei Lavrov, the Russian foreign minister, said that Ukraine had presented Moscow with a draft peace deal containing "unacceptable" elements.
According to Lavrov, the draft said the status of Crimea – which Moscow annexed from Ukraine in 2014 – should be raised at a meeting between the two countries' presidents. It also said Ukraine could hold military drills with foreign countries without receiving Russia's permission – something with which Moscow disagrees.
It came as a senior US general said the battle in eastern Ukraine would be crucial.
"There is a significant battle yet ahead down in the southeast, down around the Donbas, Donetsk region where the Russians intend to mass forces and continue their assault," Gen Mark Milley, the chairman of the Joint Chiefs of Staff, said. "I think it is an open question right now how this ends."
It is understood Russia hopes to encircle Ukrainian forces in the east and inflict heavy losses on some of its most well-trained troops to prevent reinforcements returning to defend key Ukrainian cities such as Kyiv and Odesa.
This could in turn lead to a renewed attempt by Russia to capture the Ukrainian capital, a plan that was abandoned after Russian soldiers encountered fierce resistance.
Western officials believe the next few weeks of fighting in eastern Ukraine will be pivotal in deciding the outcome of the war. A Ukrainian victory in the Donbas, which would depend on Western allies quickly supplying more weapons, raises the prospect that they could eventually push all Russian forces out of the country.
Conversely, a defeat of Ukraine's most battle-hardened soldiers would leave southern and central Ukraine exposed to a rapid takeover by Russian troops and further atrocities against the civilian population.
In its daily intelligence assessment of the war, the UK defence ministry said low morale, as well as shortages in supplies and manpower, would hamper Russia's assault in the east.
If the fight for Ukraine's eastern Donbas region does become like World War II, it may favour the Ukrainians.
Russian forces repositioning from the north and around Kyiv will find a mostly rural area, ideal for armoured warfare and the intelligent application of extreme violence. Ukrainian forces know the geography and will use it to their advantage.
Bridges have been destroyed, channelling any advancing Russian columns to fixed routes that favour counter-attacks.
The time taken to cover the distances involved will require the Russian air force to recommence operations in daylight – a boon to Ukrainian troops with shoulder-launched anti-aircraft missiles.
New weapons, gifted by the West, will be used to wear down Russia's attacking formations, long before they get into the close "contact battle" with the defenders.
Western officials said 29 of Moscow's original 125 battalion tactical groups have been rendered "not combat effective" because of the dogged Ukrainian resistance.
It means the fight to come in the east of the country could play to Ukraine's strengths if Kyiv's troops plan correctly. Ukraine will seek to use the 10 brigades dug deep in the Donbas as an anvil upon which to smash the Russian invaders.
Just as they have done fighting the Russians in the north, Ukraine will employ the Western doctrine of the "manoeuvrist approach".
This is more than just using movement on the battlefield. It describes a nimble military mind, an ability to use initiative instead of constantly relying on orders and a willingness to do the unexpected and take risks.
In the north, Ukraine's armed forces had the confidence to allow Russian tank columns to pass, choosing instead to attack the logistic tails first then pick off the stranded vehicles.
Rather than meeting Russian strength head-on, they applied devastating military force at critical points, achieving results disproportionate to the numbers of troops involved.
The open spaces of the Donbas, away from urban areas populated by civilians and where Russia will have extended lines of vulnerable logistic elements, are ideal for these tactics. The distances are vast.
And where to put their all-important logistic tail that has proved so vulnerable to the Ukrainian anti-tank teams moving nimbly across the battlefield to strike at times and places of their choosing?
In July 1943, the German army launched a major armoured offensive, Operation Citadel, against the Soviet Union near this area of eastern Europe. The Germans were tired and stretched, fighting at the end of long and vulnerable lines of logistics, but still trolled the dice and decided to attack.
They lost the battle, never meaningfully advanced again – and eventually lost the war.
The site was used by Hezbollah to plan attacks on Israeli civilians.