How Russia’s Steady Advance Threatens Ukraine’s East

Russia is closing in on a key city in Ukraine’s East in one of the fastest advances for its military since the early days of the war. If Russia captures the city, Pokrovsk, it would gain a big strategic advantage in seizing the rest of the Donbas region.

Pokrovsk is at the center of many of the rail and road lines for the whole of the Donbas. A successful Russian assault would cut the main supply lines for troops in the remaining Ukrainian strongholds across the region, and would position Moscow’s forces to menace Ukrainian positions to the south of the city.

The challenges are daunting for Ukraine. At times in August, its troops were falling back more than a mile a day.

Two dense lines of Ukrainian fortifications remain between the frontline and the city, with anti-tank ditches to slow advancing Russian vehicles and dozens of circular trenches to protect infantry and mortar units.

Over the past week, Ukraine has sent extra troops to defend the lines around Pokrovsk. Russia has pivoted from a frontal attack toward the city to assaults to the south, to broaden the front and threaten an encirclement of Ukrainian troops between Pokrovsk and the town of Kurakhove. The semi-circle Russia has formed in the area is a tactic known as creating a “cauldron.”

The advance toward Pokrovsk was the most successful part of Russia’s offensive in the Donbas this summer. Elsewhere, it attacked along most of the eastern frontline but after months of fierce fighting made only modest gains. A yearlong assault toward the hilltop town of Chasiv Yar, for example, has advanced about three miles.

While the frontline moved quickly over the summer around Pokrovsk, the overall Russian offensive in the Donbas has been costly and incremental.

Meanwhile, Ukraine launched its surprise invasion of the Kursk region in August. It captured more territory in Russia in a month than Russia has in Ukraine over the past year, though its hold on its gains in Russia have yet to be tested in a serious counterattack.

But Russia has continued to push forward in the Donbas, and President Vladimir V. Putin has said that the Russian army would not divert forces from the area to counter the Ukrainian advance in Russia.

This fast-moving phase of the war, though, may wrap up with fall rains that limit movement on both sides as all but paved roads become muddy tracks all but impassable for heavy vehicles.