participation in the Baltic Sea trade, primarily with herring, grain, and timber; craftsmanship also prospered, and more than forty guilds were established in the city. The far-reaching autonomy granted by the House of Griffins was in part reduced when the dukes reclaimed Szczecin as their main residence in the late 15th century. The anti-Slavic policies of German merchants and craftsmen intensified in this period, resulting in measures such as bans on people of Slavic descent joining craft guilds, a doubling of customs tax for Slavic merchants, and bans against public usage of their native language. The more prosperous Slavic citizens were forcibly stripped of their possessions, which were then handed over to Germans. In 1514, the guild of tailors added a Wendenparagraph to its statutes, banning Slavs. While not as heavily affected by medieval witchhunts as other regions of the empire, there are reports of the burning of three women and one man convicted of witchcraft in 1538. In 1570, during the reign of John Frederick, Duke of Pomerania, a congress was held at Stettin ending the Northern Seven Years' War. During the war, Stettin had tended to side with Denmark, while Stralsund tended toward Swedenas a whole, however, the Duchy of Pomerania tried to maintain neutrality. Nevertheless, a Landtag that had met in Stettin in 1563 introduced a sixfold rise in real estate taxes to finance the raising of a mercenary army for the duchy's defence. Johann Friedrich also succeeded in elevating Stettin to one of only three places allowed to coin money in the Upper Saxon Circle of the Holy Roman Empire, the other two places being Leipzig and Berlin. Bogislaw XIV, who resided in Stettin beginning in 1620, became the sole ruler and Griffin duke when Philipp Julius, Duke of Pomerania died in 1625. Before the Thirty Years' War reached Pomerania, the city, as well as the entire duchy, declined economically due to the decrease in importance of the Hanseatic League and a conflict between Stettin and Frankfurt an der Oder. 17th to 18th centuries Following the Treaty of Stettin of 1630, the town (along with most of Pomerania) was allied to and occupied by the Swedish Empire, which managed to keep the western parts of Pomerania after the death of BogislawXIV in 1637. From the Peace of Westphalia in 1648, Stettin became the Capital of Swedish Pomerania. Stettin was turned into a major Swedish fortress, which