Key Takeaways from the ISW : Russian forces are struggling to advance on the northern part of Ukraine’s Fortress Belt following the onset of the Russian Spring-Summer 2026 offensive. The recent Russian tactical gains could support offensive operations to the north against Lyman or to the south against Kostyantynivka, but so far are insufficient for a drive directly on Slovyansk itself. Russian forces conducted another massive strike against Ukraine on the night of March 28 to 29, striking a