In battlefields in the rolling hills of the Donbas in eastern Ukraine, and near the Black Sea in the south, Ukrainian troops have stubbornly tried to inch forward without losing control of territory, facing an opponent whose forces have been bolstered by inmates-turned-fighters and by Iranian drones.

"Perhaps it seems to someone now that after a series of victories we have a certain lull,” Ukrainian President Volodymyr Zelenskyy said in his nightly address Sunday. "But this is not a lull. This is preparation for the next sequence.”

Over the weekend, Ukraine’s army built up the pressure in the country’s south, with forces striking Russian military strongholds and targeting sites used by local officials loyal to the Kremlin. They are also continuing to hit the supply lines for thousands of Russian soldiers on the western bank of the Dnieper River. Ukraine’s strikes in the important Russian-held city of Kherson seemed to rattle security there, with firefights and broad disorder reported.