Richelieu had continued the work of Henry IV.; and Chancellor Oxenstiern did not leave to perish that of his master and friend. Scarcely was Gustavus Adolphus dead when Oxenstiern convoked at Erfurt the deputies from the Protestant towns, and made them swear the maintenance of the union. He afterwards summoned to Heilbronn all the Protestant princes; the four circles of Upper Germany (Franconia, Suabia, the Palatinate, and the Upper Rhine), and the elector of Brandenburg alone sent their representatives; but Richelieu had delegated M. de Feuquieres, who quietly brought his weight to bear on the decision of the assembly, and got Oxenstiern appointed to direct the Protestant party; the Elector of Saxony, who laid claim to this honor, was already leaning towards the treason which he was to consummate in the following year; France at the same time renewed her treaty with Sweden and Holland; the great general of the armies of the empire, Wallenstein, displeased with his master, was making secret advances to the cardinal and to Oxenstiern; wherever he did not appear in person the Imperial armies were beaten. The emperor was just having his eyes opened, when Wallenstein, summoning around him at Pilsen his generals and his lieutenants, made them take an oath of confederacy for the defence of his person and of the army, and, begging Bernard of Saxe-Weimar and the Saxon generals to join him in Bohemia, he wrote to Feuquieres to accept the king’s secret offers.
Amongst the generals assembled at Pilsen there happened to be Max Piccolomini, in whom Wallenstein had great confidence: he at once revealed to the emperor his generalissimo’s guilty intrigues. Wallenstein fell, assassinated by three of his officers, on the 15th of February, 1634; and the young King of Hungary, the emperor’s eldest son, took the command-in chief of the army under the direction of the veteran generals of the empire. On the 6th of September, by one of those reversals which disconcert all human foresight, Bernard of Saxe-Weimar and the Swedish marshal, Horn, coming up to the aid of Nordlingen, which was being besieged by the Austrian army, were completely beaten in front of that place; and their army retired in disorder, leaving Suabia to the conqueror. Protestant Germany was in consternation; all eyes were turned towards France.