WASHINGTON — Nearly 1 million Russian troops have been killed or wounded in the country’s war against Ukraine, according to a new study, a staggering toll as Russia’s three-year assault on its neighbor grinds on.

The study, published Tuesday by the Center for Strategic and International Studies in Washington, said that close to 400,000 Ukrainian troops have also been killed or wounded since the war began. That would put the overall casualty figure, for Russian and Ukrainian troops combined, at almost 1.4 million.

Officials cautioned that casualty figures were difficult to estimate because Russia is believed to routinely undercount its war dead and injured, and Ukraine does not disclose official figures. The study published Tuesday relied on casualty figures compiled by U.S. and British government estimates.

The figures present an overall accounting of Russia’s slow progress in Ukraine, with Russia proceeding in some places at about 165 feet a day, slower than even the bogged-down and costly Somme advance of British and French troops in World War I.

Since January 2024, Russia has seized less than 1% of Ukrainian territory, according to CSIS, even as it continues to advance in the country. Overall, Russia occupies about 20% of Ukraine.