Hard choices as Ukraine faces worst crisis since war began

Ukraine's second biggest city, Kharkiv, which is just 20 miles from the Russian border, is under attack and Russia's soldiers are advancing.

Ukrainians are having to make some very hard choices about what they can defend, and they are fighting an enemy that has adapted itself to exploit their weaknesses.

BBC international editor Jeremy Bowen explains why Ukraine is facing its worst crisis since Russia's invasion.