At the height of the campaign, Ukrainian forces controlled some 500 square miles of Russian territory. Now they hold just a small sliver of land along the border.

A Russian service member walks past destroyed buildings in the town of Sudzha, which was recently retaken by Russia's armed forces in the course of Russia-Ukraine conflict in the Kursk region, Russia,

Ukrainian soldiers fighting in Russia's Kursk region have described scenes "like a horror movie" as they retreated from the front lines. The BBC has received extensive accounts from Ukrainian troops,