Russia will likely surpass 1 million casualties in its war on Ukraine this summer, according to one of the world’s leading think tanks.

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.

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.