The effect of the raid, however, had been to unsettle some of the East Anglian Danes, who had given the besiegers of Rochester assistance. The English fleet made a retaliatory raid along the East Anglian coast, and captured sixteen ships at the mouth of the Stour, but was then defeated. It was clearly as yet too weak for its work. Failing to obtain satisfaction from Guthrum or his jarls, Alfred next year attacked the ‘Danelaw’ by land. After severe fighting, London was retaken, and south-eastern Mercia overrun as far as the Lea and Great Ouse. Alfred’s conquests were definitely confirmed to him next year by a treaty with Guthrum. The Roman walls of London were repaired, and the city occupied by a strong military colony. The result of these successes was that not only the Mercians under Ealdorman Aethelred, but also the princes of Wales, formally paid homage to Alfred. He strengthened the tie with Mercia by giving Aethelred his daughter Aethelflaed to wife. He also placed him in charge of the reconquered districts, which had been mainly Mercian; but evidently not for that reason, but as a personal possession. The English were at last beginning to draw together. For six years Alfred was able to pursue his life-work in peace. The East Anglian Danes observed the treaty of 886; those of Northumbria also had a Christianized chief, Guthred by name, who kept the peace with Alfred, and when the Vikings again attacked him he was well prepared. In 891 the Northmen were heavily defeated by Arnulf, King of the East Franks, at Louvain. Thereupon they resolved to turn upon England. They gathered from all quarters to Boulogne, and there remained for several months collecting and building ships. They now, on their short voyages, carried their horses with them, and had done so in the raid of 885. In all they mustered 250 ships, and, perhaps, 10,000 men. A second fleet of eighty ships under Hæsten, the most famous of the Scandinavian sea-kings, assembled farther south. The connection between the two hordes is not clear. Professor Oman suggests that while their action may have been concerted, it is possible that the leaders of the larger force held aloof from Hæsten owing to his selfishness and greed. The evidence of the campaign that followed gives the impression that the two forces acted in concert. Alfred had also to fear that the settlers of the Danelaw would join the invaders against him. Guthrum of East Anglia had died in 890, and the friendly chief of Deira was associated with a certain Siegfred who was hostile to Alfred. For the present the settlers gave hostages to Alfred as a pledge that they would keep the peace, but they broke it without scruple when occasion offered.