Russian advances could give it a shot at Ukraine's eastern 'fortress belt,' war analysts warn

• Russian forces are poised to advance toward the "fortress belt" of four eastern Ukrainian cities.
• The cities are a stronghold for Ukraine in Donetsk Oblast just northwest of Avdiivka.

Russian troops appear to be making tactical advances just northwest of Avdiivka toward a so-called "fortress belt" of Ukrainian cities, war analysts report.

Though it remains to be seen whether Russian command will turn its focus its troops on that area, they're setting the stage for offensive operations in that direction. And they've long aimed to capture these four cities.

With Russian forces continuing to solidify their positions northwest of Avdiivka, a war-torn town they captured in February, they now have choices on which objectives to pursue. Ukraine has repeatedly warned that Russia seeks to capture Pokrovsk, southwest of Bakhmut.

But according to a new assessment from The Institute for the Study of War, a Washington DC-based think tank that has followed the conflict closely, Russia has the option "to conduct possible complementary offensive operations" around Chasiv Yar, a city near Avdiivka that "is operationally significant because it would provide Russian forces with a staging ground to launch offensive operations" near two of the "four major cities that form a fortress belt" for Ukraine in the Donetsk Oblast.

Chasiv Yar, another town under tremendous pressure, is close to Duzhkivka and Kostyantynivka, the two southernmost cities in the belt. The other two, Slovyansk and Kramatorsk, are located a bit more north, but still along the same highway.

"The Russian military command could decide that advances north along the H-20 highway would allow Russian forces to conduct subsequent complementary offensive operations from the east and south against the southern edge of the Ukrainian fortress belt in Donetsk Oblast," ISW wrote.

But the effort wouldn't be rapid or easy for Russia, the analysts added. And they may still yet decide to prioritize advancing toward the west, going after the borders of Donetsk Oblast, rather than heading northwest out of Avdiivka towards the fortress belt.

At the moment, ISW reported, Ukrainian officials say Russia has deployed as many as four brigades, "roughly a reinforced division's worth of combat power," northwest of Avdiivka to stabilize sections of the front and support penetration operations.

The Russian situation is not without its challenges though.

Ukraine appears to have slowed down Russian gains near Avdiivka with reconstituted reinforcements in the area, despite facing a severe manpower shortage and disadvantages overall. That said, in recent days, Ukrainian military officials have acknowledged Russian tactical gains in the area, reporting a dire situation as they wait for the arrival of US aid.

The potential for advances in this sector comes ahead of an expected Russian offensive this summer, when Moscow's troops could have the opportunity to make significant gains in the Chasiv Yar area and beyond.

At this time, it remains unclear what weapons packages and security assistance Ukraine will have received by then and whether the country's forces will be able to sufficiently defend against a Russian offensive.