WASHINGTON, United States, Jan 28, 2026 (BSS/AFP) - Russia's grinding invasion of Ukraine has caused nearly two million military casualties -- killed, wounded or missing -- between the two countries, according to a study published Tuesday by a US think tank.

Moscow's forces have borne the brunt of the losses, suffering as many as 325,000 killed out of an estimated total of 1.2 million casualties since invading Ukraine nearly four years ago, the Center for Strategic and International Studies (CSIS) found.

"No major power has suffered anywhere near these numbers of casualties or fatalities in any war since World War II," CSIS said, noting that "Russian forces are advancing remarkably slowly on the battlefield."

Ukrainian forces have also suffered major losses -- between 500,000 and 600,000 casualties, of which between 100,000 and 140,000 were killed -- from February 2022 to December 2025, the think tank said.

"Combined Russian and Ukrainian casualties may be as high as 1.8 million and could reach two million total casualties by the spring of 2026," CSIS said.

In February 2025, Ukrainian President Volodymyr Zelensky told a US television outlet that his country had lost nearly 46,000 troops since 2022 -- a figure that analysts consider an underestimate -- while tens of thousands of others were missing or had been taken prisoner.

The BBC's Russian service and the Mediazona outlet, which rely on publicly available data such as death notices, have identified more than 163,000 Russian soldiers killed in four years of war, while acknowledging that the actual number is likely higher.

The war has also taken a heavy toll on civilians, with United Nations monitors recording more civilian deaths in Ukraine in 2025 than in any other year except 2022.

More than 2,500 civilians were killed and over 12,000 wounded in 2025, the Office of the UN High Commissioner for Human Rights said, noting that the UN has verified almost 15,000 civilian deaths since 2022, but that the total "is likely considerably higher."