The civil war era of Norwegian history lasted from 1130 to 1217. During this period there were several interlocked conflicts of varying scale and intensity. Although weak in the beginning, the Birkebeins had the upper hand in the dispute almost all the time it existed. King Haakon IV was the ultimate victor for the Birkebeins in 1217.
The background for these conflicts were the unclear Norwegian succession laws, social conditions and the struggle between Church and King. There were then two main parties, firstly known by varying names or no names at all, but finally condensed into parties of Bagler and Birkebeins.
The rallying point regularly was a royal son, who was set up as the head figure of the party in question, to oppose the rule of the king from the contesting party.
From a socio-historical perspective, scholars have interpreted the party as the result of the rapid increase in landless markamenn (meaning "border men"), who settled along the Swedish border and made their living by pillaging the rich old settlements. It was this lawless population that became the foremost basis of the birkebeiner, even though it is questionable whether their leaders were paupers wearing shoes made of birch bark.
Their leadership came from Trøndelag, a region where the social tensions were not as marked, and their motive was rather to stop the transition of power from Trøndelag to Viken and Vestlandet. The powerful Trønder families were simply being left behind by their peers in the south, who had acquired a strong leader in the Vestland earl Erling Skakke in the mid-12th century. In the early 1160s, Erling had taken control of Viken and the bishopric of Nidaros and had subsequently made his underage son Magnus Erlingsson the king of Norway. The party that was behind their rule was not called the Bagli party (Bagler) during their time, but only later.
After some initial victories of Viken party, the tables turned when Sverre entered the political scene claiming to be the illegitimate son of king Sigurd Munn. Sverre sought assistance from the Swedish earl Birger Brosa who sent him Swedish forces after some hesitation. One of Birger Brosa's sons, Filip, became Sverre's earl.
Under Sverre's leadership, the Birkebeiner movement was re-organized and pruned and the most criminal elements were brutally purged from the party. The army consisted more and more of mercenaries from Sweden and England.
As early as 1177, Sverre was proclaimed king by his followers, but in reality his power did not extend beyond the borders of Trøndelag and it took two decisive battles in 1179 and 1184 before he could be formally elected king. By then, both the main opponents were dead, i.e. earl Erling (1179) and king Magnus Erlingsson (1184), and the opposition was greatly reduced.
The Birkebeiner's political program was a continuation of earl Erling's centralization which underscores the geographical motivations behind the movement. Their leadership did not seek a social revolution, only to move the centre of power back to Trøndelag.
Around the year 1200, the rival groups shared the identical but opposite goal of controlling the entire country. In 1202, when King Sverre died, he had managed to acquire most of Norway, but in Østerdalen, the Baglers were still very powerful. Sverre's death meant some decrease in power of Birkebeins. His successor, King Haakon Sverresson, died only two years later, leaving his son Haakon Haakonsson as the ultimate target for the Baglers to get rid of the pretender to the throne. In 1206, the Birkebeiners set off on a dangerous voyage through treacherous mountains and forests, taking the now two-year-old Haakon Haakonsson to safety in Trondheim. Norwegian history credits the Birkebeiners' bravery with preserving the life of the boy who later became King Haakon Haakonsson IV, ended the civil wars in 1240 and forever changed Northern Europe's history through his reign.
The Birkebeins managed to hold some power, despite short reigns of their monarchs, and in 1209 a resolution was made between Bagler and Birkebeiner, which recognized Bagler pretender Philip as ruler of Opland and Vigen without the title of king, and recognized Birkebeiner's Inge Baardsson as king. They both died in 1217 and Birkebeiner-born Haakon IV ascended the throne, relatively unopposed, under the regency of Duke Skule.
The city arms of Lillehammer show a Birkebeiner skiing in honour of the historic rescue. The mascots Håkon and Kristin of the 1994 Winter Olympics are depicted as Birkebeiner children, bearing the names of the son and daughter of king Sverre
Near Drammen, the sports association Idrettsforeningen Birkebeineren took their name from the party.