Gustavus Adolphus’s campaigns in Livonia culminated in 1621 in the seizure of the great port of Riga, an event of European significance. Three years previously Bohemia had risen in revolt against its king, the Emperor’s cousin Ferdinand, declared him deposed and chosen in his place the Calvinist Frederick V, Elector Palatine. This act precipitated a war which was to rage across central Europe for thirty years and which was to involve, in one way or another, all the powers around the Baltic. Denmark’s entry into the struggle, motivated partly by jealousy of Sweden’s growing power to the east, proved disastrous and left the field open for its rival. After nearly twenty years of campaigning, Sweden was in a position, when peace finally returned in 1648, to establish itself firmly on the southern shore of the Baltic as not only the leading Baltic power but as one of the leading European powers. In all these developments Muscovy played only a peripheral role.