Once horses were domesticated, then large herds of horses could be bred and maintained for food, transportation and riding horses. Not all groups of people had horses however. Some groups had learned to use horses as part of their conquest of new territory. The target was often a group of people that did not have horses or using them for warfare. A group of horses racing towards you would have been terrifying!
One of the most terrifying figures of history was the leader of the Mongols, Genghis Khan. In the year 1206, when Genghis Khan was proclaimed leader, he sent trained armies out in all directions in conquest of new lands and expanded his territory to a degree never seen before! Never before had horses been used in this way to cover 100’s of miles of territory so that new lands could be taken in battle.