By the early 17th century, Sweden controlled not only Estonia but the whole Baltic Sea. It is easy to forget that Sweden was once a large empire, controlling much of Northern Europe. Under the reign of Gustavus Adolphus, the objective of Sweden’s foreign policy was dominion over the coasts of the Baltic Sea, dominium maris baltici. After the Swedes gained control of Pärnu in northern Livonia, Gustavus turned his attention to Riga. It was here that Wrangel’s officers would wield their might. The king’s troops arrived in the summer of 1621 and, after a siege of just over a month, Riga finally surrendered.