 In 851 an exceptionally large invasion force of Danes arrived at the mouth of the Thames in a fleet of about 350 ships, which would have carried over 15,000 men.Having sacked Canterbury and London and defeated King Beorhtwulf of Mercia in battle, the Danes crossed the Thames into Surrey, but were slaughtered by a West Saxon army led by King Æthelwulf in the Battle of Aclea, bringing the invasion to an end.Two years later the men of Surrey marched into Kent to help their Kentish neighbours fight a raiding force at Thanet, but suffered heavy losses including their ealdorman, Huda.