The Battle of Lubieszów, occurred on April 17, 1577, was the most important battle in the two-year Danzig Rebellion fought between the forces loyal to the newly elected King Stefan Batory of the Polish–Lithuanian Commonwealth and the Commonwealth's richest city, Danzig, following the city's refusal to accept the election of Batory as monarch of the Commonwealth which had taken place on December 15, 1575. Wikipedia