Vikings would give no trouble at all to any of the major powers during this era or any earlier ones it's not that's sophisticated but in this time period siege warfare is sort of you know at a low point. In an 868 the king of Mercia who had asked for help from the king of Westics and who brought his army into the both their armies sort of face off with the Vikings. The Mercians pay them to leave so they go back to their main base which is now north umbria. They'd put a puppet king on the throne but they do whatever they want, he says.