Swedish Baltic Expansion in the 1620s

Timeline

1. 1621–1622Riga · LatviaIn September 1621 Gustavus Adolphus led Swedish forces to besiege Riga, and over the following two years consolidated control of the Estonian and Livonian coasts, giving Sweden the most important trade port and military base on the eastern Baltic coast.
2. 1625–1626Polish-Prussian frontier · PolandAfter 1625 Swedish forces extended the war into the Polish heartland, gaining ground on the Prussian frontier in 1626, further threatening Poland's sea outlets and Danzig trade; Sweden's Baltic hegemony extended from the eastern coast toward the southwest.
3. 1629Altmark · GermanyIn September 1629 Sweden and Poland signed the Treaty of Altmark, retaining Estonia, most of Livonia, and tariff revenues from ports such as Danzig, formally establishing Sweden's dominance on the eastern Baltic coast and freeing forces for the German theater.
4. 1628–1630Pomerania · PomeraniaBetween 1628 and 1630 Sweden established a military presence in Pomerania and coordinated with German princes such as Brandenburg, completing the strategic groundwork for Gustavus Adolphus's landing at Stralsund in 1630 and formal entry into the Thirty Years' War.