“I don’t know if I have a right to tell you the numbers of our losses. Every single person is a tragedy,” he said, adding, “31,000 [members] of Ukraine’s military were killed during this war.”

The last time Ukraine publicly disclosed the number of troops lost was in December 2022, when an adviser to Zelensky said that up to 13,000 troops had been killed. Kyiv keeps casualty figures closely guarded so as to not dampen public morale. But the numbers were believed to have climbed significantly as Ukraine fought to push back Russian forces and several battles settled into grinding stalemates.

Zelensky also said that Russia had suffered 500,000 casualties, including 180,000 troops killed in action, but neither figure could be independently verified.

Last year, a leaked Pentagon document labeled top secret and dated Feb. 21, 2023, included an assessment of military casualties. It said U.S. officials believed that between 15,500 and 17,000 Ukrainian soldiers had been killed, with an additional 106,500 to 110,500 wounded.

The same assessment said that between 35,000 and 42,500 Russian soldiers had been killed and 150,500 to 177,000 had been wounded. Those figures were in line with recent assessments by Western officials, who have said that more than 200,000 Russian soldiers probably have been killed or wounded.