During much of the medieval period, fleets or “king’s ships” were often established or gathered for specific campaigns or actions, and these would disperse afterwards. These were generally merchant ships enlisted into service. Unlike some European states, England did not maintain a small permanent core of warships in peacetime. England’s naval organization was haphazard and the mobilization of fleets when war broke out was slow. In the 11th century, Aethelred II had an especially large fleet built by a national levy. During the period of Danish rule in the 11th century, the authorities maintained a standing fleet by taxation, and this continued for a time under Edward the Confessor, who frequently commanded fleets in person. After the Norman Conquest, English naval power waned and England suffered naval raids from the Vikings. In 1069, this allowed for the invasion and ravaging of England by Jarl Osborn (brother of King Svein Estridsson) and his sons.