By the early twelfth century, rumors from merchants about Vinland were circulating, with the Byzantinesformally finding about it first (in 1101). Merchant ships from England, however, had been picking up messages from Norwegian drifters since the mid 1000's. After this was reported to the English king, he believed that Norway didn't deserve this land in the eye of god, and began a blockade of their main ports.
Norway saw this as an immediate threat to their kingdom, and believed that the English would attempt to invade. Their king sent 250 soldiers down to the ships to battle out control of the ports. England retaliated, and sent more ships down to their ports, mostly full of soldiers. Battles broke out at each of these ports immediately, which led Norway to send down more soldiers to these areas.
A war formed, with the main front taking up the whole Norwegian coast. This series of sporadic battles mostly resulted in England winning them, which lowered the Norwegian army significantly. The war lasted until 1108, when Norway surrendered and allowed the English to use their port cities at will.