To strike the region with terror, he burned the capital city of Bulgaria and put all the inhabitants to the sword.

Early in the spring of the year 1238, with an army, say the ancient annalists, "as innumerable as locusts," he crossed the Volga, and threading many almost impenetrable forests, after a march, in a north-west direction, of about four hundred miles, entered the province of Rezdan just south of Souzdal.

He then sent an embassage to the king and his confederate princes, saying: "If you wish for peace with the Tartars you must pay us an annual tribute of one tenth of your possessions." The heroic reply was returned, "When you have slain us all, you can then take all that we have." Bati, at the head of his terrible army, continued his march through the populous province of Rezdan, burning every dwelling and endeavoring, with indiscriminate massacre, to exterminate the inhabitants.

City after city fell before them until they approached the capital.

This they besieged, first surrounding it with palisades that it might not be possible for any of the inhabitants to escape.
The innumerable host pressed the siege day and night, not allowing the defenders one moment for repose.