 Complete the following phrase:  Sweden held, for a time, control of the principal trade routes of the Baltic; and the increment of revenue resulting from this commanding position was of material assistance during the earlier stages of the war in Germany, whither the Swedish king Gustavus II Adolphus transferred his forces in June 1630. Gustavus, later to be called the Lion of the North due to his skills as a commander, intervened on the Protestant side in the German civil war. Using new military techniques such as lighter and more mobile artillery, a larger proportion of his infantry using firearms as opposed to pikes, and cavalry shock tactics, he won a crushing victory at the 