Complex sentence: The square was the site of a massacre of Swedish nobleman by Danish King Christian II on 7 November 1520, and the consequential revolt by Swedes led to Sweden's establishment as a sovereign state.
Split into simpler sentences: The square was the site of a massacre of Swedish nobleman by the Danish King, Christian II, on 7 November, 1520. The consequential revolt by Swedes led to Sweden's establishment as a sovereign state.