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.

The cannonade continued after nightfall, but in the darkness a body of Imperialist horsemen under Colonel Cronenberg dashed out at full speed through the gate, cut a passage through the musketeers in the suburb, galloped up the hill, and fell upon the infantry and artillery in the battery. So furious was their charge that the greater part of the defenders of the battery were cut down. The guns were spiked, and the cavalry, having accomplished their purpose, charged down the hill, cut their way through the suburb, and regained the town.

This gallant exploit deranged the plans of the Swedes. Gustavus reconnoitred the town accompanied by Sir John Hepburn, and by the advice of that officer decided upon a fresh plan of operations. Hepburn pointed out to him that by taking possession of the angle formed by the confluence of the Wermitz and Danube to the west of the town the bridge crossing from Donauworth into Bavaria would be completely commanded, and the garrison would be cut off from all hope of escape and of receiving relief from Bavaria.

The plan being approved, Hepburn drew off his brigade with its artillery, and marching five miles up the Danube crossed the river at the bridge of Hassfurt, and descended the opposite bank until he faced Donauworth. He reached his position at midnight, and placed his cannon so as to command the whole length of the bridge, and then posted his musketeers in the gardens and houses of a suburb on the river, so that their crossfire also swept it.

The pikemen were drawn up close to the artillery at the head of the bridge. Quietly as these movements were performed the garrison took the alarm, and towards morning the duke, finding his retreat intercepted, sallied out at the head of eight hundred musketeers to cut his way through; but as the column advanced upon the bridge the Green Brigade opened fire, the leaden hail of their musketeers smote the column on both sides, while the cannon ploughed lanes through it from end to end. So great was the destruction that the Bavarians retreated in confusion back into the town again, leaving the bridge strewn with their dead.

Alone the gallant Duke of Saxe-Lauenburg charged through the hail of fire across the bridge, fell upon the pikemen sword in hand, and cutting his way through them rode away, leaving his garrison to their fate. The roar of artillery informed Gustavus what was going on, and he immediately opened fire against the other side of the town and led his men to the assault of the gate.

The instant the Scotch had recovered from their surprise at the desperate feat performed by the duke, Hepburn, calling them together, placed himself at their head and led them across the bridge. The panic stricken fugitives had omitted to close the gate, and the Scotch at once entered the town. Here the garrison resisted desperately; their pikemen barred the streets, and from every window and roof their musketeers poured their fire upon the advancing column.

The day was breaking now, and the roar of battle in the city mingled with that at the gates, where the Swedes were in vain striving to effect an entrance. Gradually the Scotch won their way forward; 500 of the Bavarians were killed, in addition to 400 who had fallen on the bridge. The rest now attempted to fly. Great numbers were drowned in the Danube, and the remainder were taken prisoners. The streets were encumbered by the heavily laden baggage wagons, and a vast amount of booty fell into the hands of the Scotch, who thus became masters of the town before Gustavus and his Swedes had succeeded in carrying the gate.