The Ukrainian army has deployed some of its best brigades to eastern Ukraine, including the 92nd and 93rd Mechanized Brigades and the 1st Presidential Brigade. But these elite Ukrainian formations might not be the biggest killer of Russian troops in the east. Under-trained, under-supplied and ambivalently led, Russians in the region are freezing to death by the dozen. Shocking videos that have circulated online in recent weeks tell a tragic story. The videos, shot by the Ukrainian brigades’ hovering drones, depict Russians in the late stages of hypothermia, so cold and sick that they barely react when the drones drop...