Russia launched its biggest missile and drone attack on Ukraine so far this year on Tuesday, according to Ukrainian authorities, cutting heat to tens of thousands of people and ending a brief reprieve agreed to by Moscow and Washington as Ukrainians grapple with plummeting winter temperatures.

In the depths of winter, as temperatures plunged to minus 20 degrees Celsius, Russia unleashed one of its most devastating aerial assaults on Ukraine, firing a record number of drones and missiles jus...