Since then, Russian forces – bolstered by thousands of North Korean troops sent by Putin-ally Kim Jong-un – have sought to claw back most of that land. The North Korean troops began arriving in Kursk from late October as part of a mutual defence pact agreed between Putin and Kim.

After clinging for more than seven months to a gradually shrinking area, Ukraine has seen its position worsen sharply in the past week.

Kyiv is trying to hang on to the territory it holds inside Russia despite fierce counterattacks by Moscow’s military.