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.

No sooner had the king marched than the Spaniards again crossed the Moselle.  The chancellor and the Duke of Weimar advanced against them.  The Dutch troops, who formed the first line of the chancellor’s army, were unable to stand the charge of the Spanish and fled in utter confusion; but the Scottish regiment of Sir Roderick Leslie, who had succeeded Sir John Hamilton on his resignation, and the battalion of Sir John Ruthven, charged the Spaniards with levelled pikes so furiously that these in turn were broken and driven off the field.

On the 26th of March Gustavus arrived before the important town and fortress of Donauworth, being joined on the same day by the Laird of Foulis with his two regiments of horse and foot.  Donauworth is the key to Swabia; it stands on the Danube, and was a strongly fortified place, its defences being further covered by fortifications upon a lofty eminence close by, named the Schellemberg.  It was held by the Duke of Saxe-Lauenburg with two thousand five hundred men.  The country round Donauworth is fertile and hilly, and Gustavus at once seized a height which commanded the place.  The Bavarians were at work upon entrenchments here as the Swedes advanced, but were forced to fall back into the town.  From the foot of the hill a suburb extended to the gates of the city.  This was at once occupied by five hundred musketeers, who took up their post in the houses along the main road in readiness to repel a sortie should the garrison attempt one; while the force on the hillside worked all night, and by daybreak on the 27th had completed and armed a twenty gun battery.

In this was placed a strong body of infantry under Captain Semple, a Scotchman.  As this battery commanded the walls of the town, and flanked the bridge across the Danube, the position of the defenders was now seriously menaced, but the Duke of Saxe-Lauenburg refused the demand of Gustavus to surrender.  The battery now opened fire, first demolishing a large stone building by the river occupied by a force of Imperialists, and then directing its fire upon the city gates.