Albrecht von Wallenstein (Wallenstein, Albrecht Wenzel Eusebius von, Herzog von Friedland, Herzog von Mecklenburg, Fürst Von Sagen), impressed by Gallas' military exploits in battles of the middle and late 1620s, entrusted him with important commands (1631–33) against Gustav II Adolf of Sweden and Bernhard of Saxe-Weimar; but Gallas, together with Ottavio Piccolomini, was instrumental in the overthrow of Wallenstein, after whose murder (1634) he obtained the supreme command of the army. Although Gallas was victor in the first of the battles of Nördlingen in 1634, carelessness and drunkenness thereafter marred his conduct of the war, and he became known as the “destroyer of armies,” especially after his disastrous campaigns of 1637, 1638, and 1644, each of which resulted in the annihilation of his troops. Eventually he was forced to resign his command.