This is a list of wars involving the Kingdom of Sweden. There are legendary accounts of Swedish kings well into prehistory and they are mentioned by Tacitus in his Germania, but St. Olof Skötkonung (995–1022) was the first ruler documented to have been accepted by both the Swedes around Lake Mälaren and by the Geats around Lake Vättern. The modern state of Sweden considers itself to have been established on 6 June 1523 by the acclamation of Gustav Vasa as king which finally ended the Kalmar Union with Denmark, although the current Swedish constitution dates to 1974.