LYSYCHANSK, Ukraine — Russian forces mounted an assault on Sunday against a key Ukrainian defensive position near two strategically important eastern cities, Ukrainian military officials said, bringing them a small step closer to encircling thousands of Ukrainian troops.
Ukrainian forces rushed reinforcements to frontline positions around Toshkivka, a small town southeast of the metropolitan area of Sievierodonetsk and Lysychansk. The Russians “had success” but were eventually held off,…