Russian Offensive Campaign Assessment, December 21, 2025 (Institute for the Study of War)

Russian forces are conducting a new cognitive warfare campaign through limited cross-border attacks across a broad part of the previously dormant northern frontline in Sumy and Kharkiv oblasts.
These two cross-border attacks likely intend to advance the Kremlin’s cognitive warfare campaign to convince the West that the frontlines in Ukraine are collapsing, such that Ukraine should concede to all of Russia’s demands.
Russian forces have not set conditions to start a new offensive across the international border in northern Ukraine.
Russian forces notably have not prepared the battlefield in northern Sumy or Kharkiv oblasts for a major ground offensive through intermediate-range strikes against Ukrainian logistics.
The Russian tactics in the assault in Sotnytskyi Kozachok are not consistent with Russian assault tactics across the theater and suggest the attack was designed to be seen.
Russian forces forcibly deported about 50 civilians from Sumy Oblast in violation of international law.
Russian forces have likely seized Siversk — a town with a pre-war population of less than 11,000 — after 41 months of fighting.
US delegations continued separate meetings with Ukrainian and Russian delegations in Miami on December 21 as the Kremlin continues to reject making compromises to end the war.
Ukrainian forces recently advanced in the border area of Belgorod Oblast and near Pokrovsk. Russian forces recently advanced in the Slovyansk-Lyman direction, in the border areas of Sumy and Kharkiv oblasts, and near Borova and Siversk.

Russian Offensive Campaign Assessment, Dec. 21, 2025 | ISW

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