Champion warfare is a common theme in Irish mythology. In the Middle Ages all able-bodied men, apart from the learned and the clergy, were eligible for military service on behalf of the king or chief. Throughout the Middle Ages and for some time after, outsiders often wrote that the style of Irish warfare differed greatly from what they deemed to be the norm in Western Europe. The Gaelic Irish preferred hit-and-run raids (the "crech"), which involved catching the enemy unaware. If this worked they would then seize any valuables (mainly livestock) and potentially valuable hostages, burn the crops, and escape. The cattle raid was often called a "Táin Bó" in Gaelic literature. Although hit-and-run raiding was the preferred tactic in medieval times, there were also pitched battles. From at least the 11th century, kings maintained small permanent fighting forces known as "troops of the household", who were often given houses and land on the king's mensal land. These were well-equipped professional soldiers made up of infantry and cavalry. By the reign of Brian Boru, Irish kings were taking large armies on campaign over long distances and using naval forces in tandem with land forces.