"Even if you're on the ground, it's very difficult for you to count casualties," said Marina Miron, a postdoctoral researcher at King's College London.

Nearly 1 million Russian soldiers have been killed or injured in the country’s full-scale invasion of Ukraine, according to a new study, a grisly measure of the human cost of Russian President’s Vladimir Putin’s unprovoked three-year assault on its neighbor.

With high casualty figures and the slow pace of Russia’s territorial gains, President Vladimir V. Putin could face years more of a grinding war of attrition in Ukraine.