[Sidenote: Alfred's plan to meet the pagans on the sea] In the year 877 the pagans, on the approach of autumn, partly settled in Exeter[259] and partly marched for plunder into Mercia.[260] The number of that disorderly horde increased every day, so that, if thirty thousand of them were slain in one battle, others took their places to double the number. Then King Alfred commanded boats and galleys, i.e., long ships, to be built throughout the kingdom, in order to offer battle by sea to the enemy as they were coming.[261] On board these he placed sailors, whom he commanded to keep watch on the seas. Meanwhile he went himself to Exeter, where the pagans were wintering and, having shut them up within the walls, laid siege to the town. He also gave orders to his sailors to prevent the enemy from obtaining any supplies by sea. In a short time the sailors were encountered by a fleet of a hundred and twenty ships full of armed soldiers, who were on their way to the relief of their countrymen. As soon as the king's men knew that the ships were manned by pagan soldiers they leaped to their arms and bravely attacked those barbaric tribes. The pagans, who had now for almost a month been tossed and almost wrecked among the waves of the sea, fought vainly against them. Their bands were thrown into confusion in a very short time, and all were sunk and drowned in the sea, at a place called Swanwich.[262] In 878, which was the thirtieth year of King Alfred's life, the pagan army left Exeter and went to Chippenham. This latter place was a royal residence situated in the west of Wiltshire, on the eastern bank of the river which the Britons called the Avon. They spent the winter there and drove many of the inhabitants of the surrounding country beyond the sea by the force of their arms, and by the want of the necessities of life. They reduced almost entirely to subjection all the people of that country. [Sidenote: Alfred in refuge at Athelney] [Sidenote: The battle of Ethandune and the establishment of peace (878)]