While the peace negotiations had been dragging on, events elsewhere in Europe of course had not stood still. While Spain was busy fighting the Mantuan war, the Swedes had intervened in the Thirty Years' War in Germany under Gustavus Adolphus in 1630, supported by French and Dutch subsidies. The Swedes used the new Dutch infantry tactics (enhanced with improved cavalry tactics) with much more success against the Imperialist forces than the German Protestants had done and so gained a number of important successes, turning the tide in the war. However, once its war with Italy ended in 1631, Spain was able to build its forces in the northern theatre of war up to strength again. The Cardinal-Infante brought a strong army up, by way of the Spanish Road, and at the Battle of Nördlingen (1634) this army, combined with Imperialist forces, using the traditional Spanish tercio tactics, decisively defeated the Swedes. He then marched immediately on Brussels, where he succeeded the old Infanta Isabella who had died in December 1633. Spain's strength in the Southern Netherlands was now appreciably enhanced.