The Treaty of Stettin (Swedish: Traktaten or Fördraget i Stettin) or Alliance of Stettin (German: Stettiner Allianz) was the legal framework for the occupation of the Duchy of Pomerania by the Swedish Empire during the Thirty Years' War. Concluded on 25 August (O.S.) or 4 September 1630 (N.S.), it was predated to 10 July (O.S.) or 20 July 1630 (N.S.), the date of the Swedish Landing. Sweden assumed military control, and used the Pomeranian bridgehead for campaigns into Central and Southern Germany. After the death of the last Pomeranian duke in 1637, forces of the Holy Roman Empire invaded Pomerania to enforce Brandenburg's claims on succession, but they were defeated by Sweden in the ensuing battles. Some of the Pomeranian nobility had changed sides and supported Brandenburg. By the end o