While Ukraine has reclaimed the capital Kyiv, the win is not "decisive" and experts believe Vladimir Putin's assault could still be successful.
The war in Ukraine has been raging for over a month and while Ukraine regaining control of Kyiv is a win and Russian troops are retreating, the Institute for the Study of War warns the war is "far from over".
In the institute's Russian Offensive Campaign Assessment from April 3, it was outlined how Russia could launch a successful operation in eastern Ukraine.
"The current line of Russian occupation in southern and eastern Ukraine is still a significant gain in Russian-controlled territory since the start of the war," the assessment said.
"If a ceasefire or peace agreement freezes a line like the current front-line trace, Russia will be able to exert much greater pressure on Ukraine than it did before the invasion and may over time reassemble a more effective invasion force.
"Ukraine’s victory in the Battle of Kyiv is thus significant but not decisive."
The institute said Russia was withdrawing troops from the east and the west banks of the Dnipro in a disorderly manner.
It is likely the Russian forces that retreated from Kyiv will need "considerable" time before they are ready for combat.
However, the withdrawal also suggests some of the units are now "reconcentrating" in western Russia and Belarus, a nation friendly with Moscow.
The 'next pivotal battle' in Ukraine
The Institute said in the update from April 4 that the next battle in the war will be in Slovyansk, as Russian forces move from Izyum.
Slovyansk sits in the Donetsk Oblast, the eastern part of Ukraine, Izyum is about 50km north of Slovyansk.
"Russian forces likely intend to cut off Ukrainian forces in eastern Ukraine and will need to take Slovyansk as their minimum step to do so," the Institute said.
#Ukrainian forces announced today that they liberated #Zhytomyr Oblast, near #Kyiv. #Russian forces continue to conduct attacks attempting to seize the town of #Rubizhne in #Luhansk Oblast.
See the latest maps from @TheStudyofWar and @criticalthreats. pic.twitter.com/58pIJsrDCa
— ISW (@TheStudyofWar) April 4, 2022
By capturing Slovyansk, Russian troops would then have the option to advance east and link up with Russian forces fighting in Rubizhne.
However, if Russian forces fail to take Slovyansk, it could mean a small victory for Ukraine.
"If Russian forces are unable to take Slovyansk at all, Russian frontal assaults in Donbas are unlikely to independently break through Ukrainian defences and Russia’s campaign to capture the entirety of Luhansk and Donetsk oblasts will likely fail," the Institute said.
US accuses Putin of war crimes
US President Joe Biden has accused his Russian counterpart of war crimes and called for a trial, after a global outcry of civilian killings in the Ukrainian town of Bucha.
Earlier this week, after Bucha was reclaimed from Russian troops, mass graves were discovered and bodies were found, showing civilians were shot at close range.
Ukrainian President Volodymyr Zelensky called the killings "genocide" in a speech from Bucha on Monday as journalists entered the city and documented its destruction.
The discovery led to the US and Europe imposing additional sanctions against Moscow.
"We have to gather the information. We have to continue to provide Ukraine with the weapons they need to continue the fight. And we have to get all the detail so this can be an actual, have a war crimes trial," Biden said.
The Kremlin categorically denied any accusations related to the murder of civilians, including in Bucha, where it said the graves and corpses had been staged by Ukraine to tarnish Russia.
Biden's National Security Advisor Jake Sullivan told reporters the US will seek information from four sources to build a case for war crimes: the US and its allies, including intelligence services; Ukrainian observations on the ground; international organisations including the United Nations; and interviews from global independent media.
He said the US would build a case at the International Criminal Court or another venue. The US is not a party to the ICC.
Russia's permanent membership in the United Nations Security Council means any war crimes accountability could be blocked by Moscow in that body, Sullivan said.
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