Ukrainian troops sprang one of the biggest surprises of the war by invading Russia's Kursk region last August, and Russia has taken more than seven months to eject them.

Russia on Sunday battled to drive the last Ukrainian soldiers from western Russia after a seven-month incursion by Ukraine that aimed to distract Moscow’s forces, gain a bargaining chip and rile President Vladimir Putin.

Russian forces have begun an assault on the town of Sudzha, the main population center in the Kursk region that was captured by Ukraine last year, a top Russian commander said on Tuesday. The advance puts Moscow on the verge of ending the first invasion of Russian territory since World War II.