Battle of Lyndanisse

The Battle of Lyndanisse or Lindanise was fought on 15 June 1219 during the Northern Crusades, between the forces of the invading Kingdom of Denmark and the local non-Christian Estonians. The Danish victory in the battle, at the site of the later Hanseatic city of Reval helped King Valdemar II of Denmark to subsequently claim the territory of northern Estonia as his participation in the crusade into Estonia had been undertaken in response to calls from the Pope.The 1219 Battle of Lyndanisse is still well known to this day, especially amongst Danes and Estonians, because of a popular legend about the first ever Danish flag, the Dannebrog, which allegedly fell from the sky, as an apparently helpful divine intervention, just when the Danish Crusaders were about to lose the battle to the local pagans.

Source: Wikipedia