President Vladimir V. Putin of Russia for months has portrayed his forces as being on the brink of victory in Ukraine.

He has suggested that he has little reason to agree to a cease-fire, seeing as Russian forces are advancing on the battlefield and are prepared to fight for the duration. He has cheered Russia’s recapture of its western Kursk region from Ukraine. And he has said, that when it comes to Ukrainian troops, Moscow has reason to believe “we are set to finish them off.”

Kyiv, over the weekend, offered its retort.

Ukraine carried out one of the most audacious attacks of the war, smuggling drones deep into the Russian heartland and launching them from semi-trucks. It destroyed or damaged at least a dozen aircraft, including many of Moscow’s nuclear-capable strategic bombers, on runways in Siberia and Russia’s Far North.

Sunday’s assault, carried out on the eve of the latest round of peace talks between Russia and Ukraine, appeared designed to send a clear message to Mr. Putin: Continuing the war still poses serious risks for Moscow, even if Ukraine is no longer able to advance on the battlefield.

“It’s all about trying to convince the Russians — whether it will succeed, I don’t know — that there is a reason now for them to negotiate seriously,” said James M. Acton, co-director of the nuclear policy program at the Carnegie Endowment for International Peace.