ILOVAISK, Ukraine — Burned-out tanks, troop carriers and trucks still lie strewn on the roads and fields all around this town. The body of a Ukrainian soldier hangs doubled over an electric wire, flung up like a doll when his tank exploded. The charred corpse of another soldier lies inside the hull of the tank, a third putrifying torso is tangled in machinery on the road.

It is vivid, if horrifying, evidence of what was a devastating offensive mounted by Russian artillery units at the end of August that smashed the government forces, breaking what had been a relentless advance that had seemed on the verge of crushing the pro-Russian uprising in the country’s southeast. Days later, Ukraine agreed to a cease-fire cementing the rebels’ hold on the region.

In a matter of five days, beginning on Aug. 28, the previously ill-equipped and inept rebels, backed or led by regular Russian troops and artillery, obliterated almost every Ukrainian position in a 20-square-mile area around this town.

Under withering and highly accurate artillery fire, entire Ukrainian units were virtually wiped out, hundreds of men were killed or wounded, and 250 were taken prisoner, according to rebel commanders. Scores of wounded have filled Ukrainian hospitals, and nearly 100 vehicles were destroyed, some in the fields and villages, others on the roads.