President Trump and President Vladimir V. Putin both claimed that Ukrainian forces were surrounded. Ukraine’s top military commander vowed to “hold the line.”

Russia said on Tuesday that its troops had made major new gains in its western region of Kursk, accelerating their push to drive out Ukrainian forces who have been clinging on to a slice of Russian territory since last August.

Russia has launched fresh attacks on multiple Ukrainian cities while reclaiming 90% of seized territory in the Kursk region. Amid the escalating conflict, President Putin made a bold visit to Kursk, ordering swift military action.