Swedish intervention in the Thirty Years' War in the context of "Peace of Prague (1635)"

The War of the Mantuan Succession, 1628 to 1631, was caused by the death in December 1627 of Vincenzo II, last male heir from the House of Gonzaga, long-time rulers of Mantua and Montferrat. Their strategic importance led to a proxy war between the French-backed Duke of Nevers, and the Duke of Guastalla, supported by Spain. It is considered a related conflict of the 1618 to 1648 Thirty Years' War.

Fighting centred on the French-held fortress of Casale Monferrato, which the Spanish besieged twice. French intervention on behalf of Nevers in April 1629 led Emperor Ferdinand II to support Spain by transferring troops from Northern Germany. They captured Mantua in July 1630, but failed to take Casale. Ferdinand withdrew his troops in response to Swedish intervention in the Thirty Years' War, and both sides agreed a truce in October 1630.

The Battle of Breitenfeld took place during the Thirty Years' War on 17 September 1631 near Breitenfeld, Leipzig, in modern Saxony. A combined Swedish-Saxon army led by Gustavus Adolphus and John George I, Elector of Saxony defeated an Imperial-Catholic League Army under Johann Tserclaes, Count of Tilly.

Swedish intervention in the Thirty Years' War began in June 1630 when nearly 18,000 troops under Gustavus Adolphus landed in Pomerania, financed by French subsidies. In early 1631, Tilly invaded Saxony after John George I made an alliance with Gustavus Adolphus. The combined Swedish-Saxon force of around 40,150 marched on Leipzig where Tilly's army of 31,400 was based.

The Siege of Stralsund, 13 May to 4 August 1628, took place during the Thirty Years' War when an Imperial Army under Albrecht von Wallenstein attempted to capture the key Baltic Sea port of Stralsund. Then an independent city and part of the Hanseatic League, Stralsund was initially reinforced by small numbers of Scots mercenaries in Danish service, before Gustavus Adolphus of Sweden sent a larger force under Alexander Leslie.

The failure of the siege ended Wallenstein's series of victories, while Straslund was held by the Swedes for most of the next two hundred years. It provided Gustavus a bridgehead within the Holy Roman Empire that in 1630 facilitated Swedish intervention in the Thirty Years' War.

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 of the war, the treaty was superseded by the Peace of Westphalia (1648) and the subsequent Treaty of Stettin (1653), when Pomerania was partitioned into a western, Swedish part (Western Pomerania, thenceforth Swedish Pomerania), and an eastern, Brandenburgian part (Farther Pomerania, thenceforth the Brandenburg-Prussian Province of Pomerania).