About the same time the important town of Ulm on the Danube opened its gates to the Swedes, and Sir Patrick Ruthven was appointed commandant with 1200 Swedes as garrison, Colonel Munro with two companies of musketeers marched to Coblentz and aided Otto Louis the Rhinegrave, who with a brigade of twenty troops of horse was expecting to be attacked by 10,000 Spaniards and Walloons from Spires. Four regiments of Spanish horse attacked the Rhinegrave's quarters, but were charged so furiously by four troops of Swedish dragoons under Captain Hume that 300 of them were killed and the Elector of Nassau taken prisoner; after this the Spaniards retired beyond the Moselle. In other parts of Germany the generals of Gustavus were equally successful. General Horn defeated the Imperialists at Heidelberg and Heilbronn. General Lowenhausen scoured all the shores of the Baltic, and compelled Colonel Graham, a Scotch soldier in the Imperial service, to surrender the Hanse town of Wismar. Graham marched out with his garrison, 3000 strong, with the honours of war en route for Silesia, but having, contrary to terms, spiked the cannon, plundered the shipping, and slain a Swedish lieutenant, Lowenhausen pursued him, and in the battle which ensued 500 of Graham's men were slain and the colonel himself with 2000 taken prisoner. General Ottentodt was moving up the Elbe carrying all before him with a force of 14,000 men, among whom were five battalions of Scots and one of English. This force cleared the whole duchy of Mecklenburg, capturing all the towns and fortresses in rapid succession. Sir Patrick Ruthven advanced along the shores of Lake Constance, driving the Imperialists before him into the Tyrol. Magdeburg was captured by General Banner, the Landgrave of Hesse-Cassel reduced all Fulda-Paderborn and the adjacent districts, the Elector of Saxony overran Bohemia, and Sir Alexander Leslie threatened the Imperialists in Lower Saxony. Thus the campaign of 1632 opened under the most favourable auspices. The Green Brigade marched on the 5th of March to Aschaffenburg, a distance of more than thirty miles, a fact which speaks volumes for the physique and endurance of the troops, for this would in the present day be considered an extremely long march for troops, and the weight of the helmet and armour, musket and accoutrements, of the troops of those days was fully double that now carried by European soldiers. Here they were reviewed by the king. By the 10th the whole army, 23,000 strong, were collected at Weinsheim and advanced towards Bavaria, driving before them the Imperialists under the Count de Bucquio. The Chancellor Oxenstiern had been left by the king with a strong force to guard his conquests on the Rhine.