Close Zelensky warns Russia is planning ‘massive’ strike ahead of peace talksOn The Ground newsletter: Get a weekly dispatch from our international correspondents Get a weekly dispatch from our international correspondents Get a weekly international news dispatch Email * SIGN UP I would like to be emailed about offers, events and updates from The Independent. Read our Privacy noticeRussian forces have suffered the heaviest battlefield losses the world has seen since the Second World War during its invasion of Ukraine, a new study shows. The Center for Strategic and International Studies says the war has resulted in about 1.2 million Russian casualties and between 500,000 and 600,000 Ukrainian casualties. “No major power has suffered anywhere near these numbers of casualties or fatalities in any war since World War II,” the CSIS said, despite advancing "remarkably slowly on the battlefield". Elsewhere, Volodymyr Zelensky has accused Russian president Vladimir Putin of an “act of terrorism” after a Russian attack on a Ukrainian passenger train killed at least five people.