The strategic goal of Ukraine's biggest cross-border incursion in almost 900 days of the war remains unclear, but it counters Russia’s unrelenting effort in recent months to punch through Ukrainian defenses at selected points along the front line in eastern Ukraine. The Russian offensive's slow, grinding momentum has achieved only modest gains and brought heavy losses of troops and armor. But, bit by bit, the advances are adding up. These summer months are critical for Ukraine and its depleted army. It must hold at bay its bigger and better-equipped enemy on the battlefield, while repairing — before winter arrives — a national power grid smashed by Russian missiles, What does Ukraine’s eastern front battlefield look like? The roughly 1,000-kilometer (600-mile) front line remains largely deadlocked. But at points in the east, especially in the Donetsk region. Russia is making a concerted push. Its army is exploiting the dry land to move its armor, the bushy tree lines for i