VOLNOVAKHA, Ukraine—On Tuesday in this embattled front-line town in eastern Ukraine, the Ukrainian army’s 30th Brigade came under 120 mm mortar fire from its enemy—a combined force of pro-Russian separatists and Russian regulars entrenched across no man’s land about 2 kilometers away.The indirect fire skirmishes in Volnovakha underscore a more widespread surge in heavy fighting along the 250-mile-long front lines in eastern Ukraine, which began on Jan. 29.
