KRAMATORSK, Ukraine—Exhausted by winter combat that has resulted in heavy casualties but few significant changes to the front line, Ukraine and Russia are preparing for spring offensives that both sides hope will shift the course of the war. As the muddy ground dries up, unpaved roads and fields will become passable again in the coming weeks, first in Ukraine’s south and then in the east, enabling both countries’ militaries to attempt breakthroughs with mobile mechanized units.

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