Ukrainian forces are under intense pressure in Russia's Kursk region, where they grabbed a chunk of land last August and have held on to it through more than seven months of fierce fighting. What's happening and why is it important?

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.