By the end of the 10th century, European magnates had realised that a man on horseback with a spear moves faster than one on foot, making him far more useful, and soon heavily armed horsemen began to take precedence over elite footmen. Even the Viking kingdoms soon learnt to use cavalry to their advantage, with their Gallicised Norman descendents soon learning to transport horses by ship to where they were needed. The cost of raising horse and rider and then arming them however was problematic to the extreme in the mostly agrarian societies of Dark Age Europe, and so it was that only people of means could furnish cavalry units to fight for their kings, meaning the ruling aristocracy (and in more modern times, yeomen as well).