Alfred’s victory at Edington gave him a unique position. He was quite a success on the battlefield, and he had routed the seemingly invincible Vikings, time and again. This last battle had even resulted in the conversion to Christianity of the Viking leader, Guthrum. Alfred was also the de facto religious leader of the Saxons, since he was also godfather–by order of the treaty signed at the completion of the Battle of Edington–to King Guthrum.
So what did Alfred do with his sudden new power? He consolidated his hold on his homelands, of course.
One of the tenets of this new “arrangement,” by which many of the invading Northmen resigned themselves to returning to their East Anglian farmsteads and actually taking up farming instead of raiding the farms of their Saxon “neighbors” was that the Saxons and the Vikings would get together and decide on boundaries for such settlements as could commonly be agreed on by two such warring armies that had tired of fighting each other. The result was the Danelaw.
This bold new demarcation gave a large part of Britannia to the Danes (and other Northmen) and left another large part of Britannia to be ruled by the Saxons. In the process, Alfred gave himself and his kingdom, Wessex, parts of what had just a few days before been parts of other Saxon kingdoms, notably West Mercia and Kent. Win a big battle and you get to keep the spoils, which in this case were land and money.
Alfred was also shrewd enough to realize that he needed to hold onto this territory. The most common way to do such a thing in those times was through a royal marriage. Alfred himself had married Eahlswith, a Mercian noblewoman, cementing the Wessex-Mercia partnership (with Wessex on top, of course). He now set about strengthening that partnership for generations to come with the marriage of one of his daughters, Aethelflaed, to the ealdorman of Mercia and another daughter, Aelfthryth, to the count of Flanders. Flanders at this time was a strong naval power, a power that the Saxons would need if the Northmen decided to improve their territory later on.
What did this mean for the rest of Saxon England? Alfred was their savior, of course. When all about them was crumbling (literally and figuratively), the young Wessex warrior had stepped into the breach, filled the dike, and brought the Vikings to bear, through power of sheer will and determination a good bit of luck. As such, he was the conquering hero, the deliverer, the savior of the realm. And as such, he could very well demand whatever he wanted from his fellows. He began with more territory and more political alliances. He would do even more.