Birka was never primarily a military installation. It was a market town, a place where merchants and craftspeople lived alongside the seasonal traders who arrived during the summer sailing months. The silver in Birka’s graves came from the Islamic world via river systems that ran through what are now Russia and Ukraine. The silk came from further east. The glass came from the Rhineland. The amber was local. The furs were regional. The people who moved these things — the traders, the agents, the craftspeople who processed raw materials into goods, the brokers who negotiated between buyers from different cultural traditions — are the people who made Birka work.
But a trading town needs protection. It needs protection from pirates. It needs protection from the political ambitions of regional powers. It needs protection from the simple fact that concentrated wealth attracts violence. The hill fort at Birka — Borgen — provided some of that protection, and the graves near it suggest that the people responsible for the town’s defense were a defined and honored social class.
Viking Age Scandinavian society was stratified, though not in the rigid feudal terms that European history applied to the same era in other regions. The distinction between a free person (*karl*) and a noble (*jarl*) was significant, and the distinction between either and an unfree person (*þræll*) was more significant still. Within the free population, military capacity and the ability to lead warriors represented a path to status that coexisted with, and often depended on, economic resources. The person who could equip a small warband and lead it on a profitable raid — or defend a settlement against one — occupied a specific and valued social position.