At the beginning of the 14th century, the Duchy of Pomerania, a neighboring region, plunged into war with Poland and the Margraviate of Brandenburg to the west. The Teutonic Knights seized the Polish port city of Gdańsk in November 1308. The Order had been called by King Władysław I of Poland to help repel a Brandenburgian invasion, however, the Teutonic Knights themselves began to occupy the city and the region. The Teutonic Knights then carried out a massacre of the inhabitants of the city, killing up to 10,000 people according to medieval sources, although the exact number of victims is a subject of disputes. In September 1309, Margrave Waldemar of Brandenburg-Stendal sold his claim to the territory to the Teutonic Order for the sum of 10,000 Marks in the Treaty of Soldin. This marked the beginning of a series of conflicts between Poland and the Teutonic Knights as the Order continued incorporating territories into its domains.