In the first phase of its war to capture Ukraine’s eastern Donbas region, Moscow’s strategy was to corral defenders in urban centers, pound them with artillery and leave them with the terrible choice of either retreating or fighting on, cut off from reinforcements and a means to escape.
The strategy enabled Russian forces to claim Luhansk, the more northeastern of the two provinces of the Donbas. In the new phase of the war, aimed at consolidating power and gaining more territory in the other province, Donetsk, President Vladimir V. Putin’s forces have already started to repeat the pattern. This time, however, making it work could prove harder.
Russian forces have been sporadically shelling in Donetsk for weeks. Shellfire killed seven civilians in the last 24 hours in Donetsk, the regional military governor, Pavlo Kyrylenko, said on Thursday.
Russia-backed separatists set up breakaway republics in both Luhansk and Donetsk in 2014 and have been fighting Ukrainian troops ever since. The battle for Luhansk began in earnest in April and reached a climax this week when the city of Lysychansk fell.
Military experts said that Ukrainian forces defended territory aggressively in Luhansk, made smart tactical decisions and even performed the difficult maneuver of retreating from Lysychansk under fire to preserve their force’s strength and avoid encirclement. In the end, though, they could not withstand Russia’s superior firepower.
“Artillery is one of the most important components of Russian operations,” said a report this week from the Royal United Services Institute, a research institute based in London, “and in terms of lethal capabilities it has become Russia’s mission-critical force multiplier.”
The Ukrainian authorities framed the fighting in similar terms. “Yes, they have an order of magnitude more forces and means,” Luhansk’s military governor, Serhiy Haidai, said on Wednesday, referring to Russia’s artillery advantage. But he argued that the situation was changing.
Western countries have increased the flow of weapons to Ukraine, including long-range missiles capable of hitting Russian positions and infrastructure. The most advanced of these is the High Mobility Artillery Rocket System, or HIMARS, supplied by the United States, the first of which have just started to be deployed.
“More long-range weapons will appear,” Mr. Haidai said, adding that “the Ukrainian Army is better prepared and motivated” than its foe.
In the war’s early stages, Mr. Putin’s forces — bewildered by the tenacity of Ukraine’s defense of its sovereign territory — failed to capture the capital, Kyiv. Moscow’s supply lines became overextended and its forces could not concentrate their artillery power effectively. Military experts said that Russia had learned from those mistakes and had applied the lessons in Luhansk, where proximity to its own border helped to shorten supply lines.
Now, in Donetsk Province, a largely flat region of heavy industry and agriculture, Russia has multiple lines of potential attack. Russian forces are advancing slowly toward the cities of Sloviansk, Bakhmut and Siversk from those they control, including the city of Donetsk in the south of the Donbas, Izium in the north and from Luhansk Province itself. Russia can also bring forces from the southern port city of Mariupol, which fell to Moscow in May.
A British intelligence report on Wednesday said that, over the past week, Russian forces had likely advanced up to five more kilometers, or about three miles, down the main road of Izium “in the face of extremely determined Ukrainian resistance.” It said Russian forces were now around 16 kilometers, or 10 miles, north of Sloviansk.
The ultimate Russian objective in the Donbas is to capture Kramatorsk, the site of Ukraine’s regional administration since 2014, when separatists seized territory in the region and established the two self-declared republics backed by Moscow. During the eight years of conflict that followed, Ukrainian forces built elaborate defensive positions designed to make Russian forces pay dearly for any further attempts to seize territory.