The Administrator immediately collected troops and commenced hostilities, before Gustavus Adolphus was near enough to co-operate with him. He defeated some imperial detachments in the neighbourhood, made a few conquests, and even surprised Halle. But the approach of an imperial army obliged him to retreat hastily, and not without loss, to Magdeburg. Gustavus Adolphus, though displeased with his premature measures, sent Dietrich Falkenberg, an experienced officer, to direct the Administrator's military operations, and to assist him with his counsel. Falkenberg was named by the magistrates governor of the town during the war. The Prince's army was daily augmented by recruits from the neighbouring towns; and he was able for some months to maintain a petty warfare with success. At length Count Pappenheim, having brought his expedition against the Duke of Saxe-Lauenburg to a close, approached the town. Driving the troops of the Administrator from their entrenchments, he cut off his communication with Saxony, and closely invested the place. He was soon followed by Tilly, who haughtily summoned the Elector forthwith to comply with the Edict of Restitution, to submit to the Emperor's orders, and surrender Magdeburg. The Prince's answer was spirited and resolute, and obliged Tilly at once to have recourse to arms. In the meanwhile, the siege was prolonged, by the progress of the King of Sweden, which called the Austrian general from before the place; and the jealousy of the officers, who conducted the operations in his absence, delayed, for some months, the fall of Magdeburg. On the 30th March 1631, Tilly returned, to push the siege with vigour. The outworks were soon carried, and Falkenberg, after withdrawing the garrisons from the points which he could no longer hold, destroyed the bridge over the Elbe. As his troops were barely sufficient to defend the extensive fortifications, the suburbs of Sudenburg and Neustadt were abandoned to the enemy, who immediately laid them in ashes. Pappenheim, now separated from Tilly, crossed the Elbe at Schonenbeck, and attacked the town from the opposite side.