The Danish Conquest of Norway was a series of wars between 1206 and 1222. This series of conflicts ended with Denmark in control of Norway, wining the war.
First War (1206-1209)
Noticing the weaknesses of Norway due to diseases brought from the New World, King Christian IX of Denmark saw the opportunity to gain land with relative ease. He called up around a thousand troops to participate in the first assault with a few hundred more in reserve. Of course, the land did not come easily at all. Despite initial gains, supply line failure and low morale forced the Danish troops to go on the defensive by mid-1208. The Danes, desperate for food, killed infected animals in Norway, starting an outbreak in their camps. These outbreaks killed at least one hundred and fifty Danish troops quite slowly. However, this resulted in an unintended side effect for the Norse; they were unable to stage any more meaningful offensives, for fear of catching the disease again.The result was a Pyrrhic victory for the Danes, and no land was gained for either side.
Second War (1211-1219)
Christian IX, of course, was not satisfied with the miniscule gains his army got him. After two years of peace at the front, he sent an additional two thousand troops to invade Norway once more by sea. This ignited the longest and bloodiest section of the conquest, which would last for eight years. The Norse were completely unprepared for a move this bold move, and as a result, their lines crumbled. This then resulted in a campaign of rapid success for the Danish until 1214. The outbreaks in Vinland got much worse during that time, meaning that military support for Norway was even less from the region. But in early 1215, the Norwegians mustered a moderately-sized army of fifteen hundred men, and engaged the thirteen hundred Danish troops occupying the capital. This became known as the Battle of Oslo. Although Oslo was still held by the Danish by the end of it, both armies suffered major casualties. An estimated eight hundred troops died, in one of the most gruesome battles of the thirteenth century. This major battle resulted in a short pause in the fighting until later in 1215, when the Danish had successfully absorbed Oslo entirely. At that point, the Danish army had been reinforced, and they went on another campaign, reaching as far north as what is now Namsos. At that point they were halted by both the weather and lack of supplies, but around this time the Norse took almost twice the amount of casualties the Danish did. By the end of the Second War, Denmark has basically absorbed Norway, with the most northern towns falling into anarchy.
Third War (1221-1222)
This "war" would best be described as a surrender. There was very minimal combat, except in the far north. Instead, Christian used the army as a diplomatic tool, pressuring the Norse into surrender by systematically seizing the remaining free towns. In the end, Norway completely surrendered and their king, Olaf II, was hanged in Copenhagen. Oslo was mostly Norwegian still, but it would not pose a threat to Denmark due to the heavy military presence there. In the end, the war was won by the Danish and Norway completely perished. Today, Norwegian culture is basically gone, having melded with the modern-day Danish one.