Both sides believe they can win on the battlefield, and little room exists for peace negotiations. Ukraine is preparing offensives to regain the roughly 18% of its territory still occupied by Moscow, including the Crimea peninsula and parts of the eastern Donbas region that Mr. Putin seized in 2014. Russia has declared four Ukrainian regions, none of which it fully controls, to be its own sovereign territory and seeks, at the very least, to conquer those lands. Mr. Putin, in a speech on Tuesday, indicated that his aspirations remain much broader, referring to Russia’s “historical territories that are now called Ukraine.”