Gustavus’ councillor Oxenstierna replaced him in the field in Germany but lost badly at First Nördlingen (September 5–6, 1634). He was later taken hostage by his own men, who demanded all pay in arrears. Sweden did not recover from this debacle for several years. Moreover, the Habsburg victory persuaded Olivares that the moment had come to throw the French off the right bank of the Rhine, where Richelieu had been planting garrisons since 1632. Spanish troops attacked the French in Trier in March 1635 (taking the archbishop prisoner), in an effort to establish an alternative route to the Spanish Road, which had been cut by France. The assault on Trier was designed to trigger war between France and the Holy Roman Empire. The stratagem failed: on May 19, 1635, France declared war only on Spain. Longer term, expanded Spanish-French fighting drew Habsburg armies away from northern Germany, permitting Sweden to slowly recover. Led by a prince of the church, Cardinal Richelieu, France finally intervened in the German war only when the gains it had earlier made by stealth in the Rhineland were assaulted and eroded by Spain. It did not enter the war as a Catholic power, as Richelieu had already signed offensive treaties with Protestant Sweden and the Netherlands in expectation of fighting Catholic Austria and Spain. Why? With Catholicism secure in France following Richelieu’s crushing of the last Huguenot military resistance in 1628, France was free to act for raison d’etat (reason of state) against the Habsburg powers rather than out of delusional confessional loyalty. Besides, France and Spain had fought an undeclared but bitter frontier war for years in northern Italy and along the Spanish Road, even after the formal end of the Mantuan war in 1631. The stunning Swedish defeat at Nördlingen confirmed Imperial control of southwest Germany and seemed to re-close a strategic ring of Habsburg lands around the perimeter of France that had been broken by Gustavus. This threat persuaded Richelieu that France must enter the war directly at long last, that fighting the Habsburgs through subsidized proxies was no longer enough. France must now intervene herself in Flanders, Germany, Italy, and at sea. For four years France pursued these grand strategic goals with an inadequate military system, with poor armies badly led by inept generals. It was not until the early 1640s that France settled on sound commanders and fielded well-trained armies capable of winning the war. It was greatly aided by the cracking of Habsburg power occasioned by the revolt of Catalonia and another in Portugal in 1640.
Louis de Bourbon, Prince of Condé (8 September 1621 – 11 December 1686)
French intervention—which guaranteed a great widening of the war— occurred just as Ferdinand and the German princes reached an accommodation that might have ended it: the Peace of Prague (May 30, 1635). However, the ‘‘German war’’ was no longer solely a German affair: it was a general war involving all the major powers, which meant it could not be ended by a settlement crafted by Germans alone. In addition, the anti-Habsburg coalition did not agree on what sort of peace it should force on the Habsburg powers, with Sweden concentrating on the German war and desperate for territorial and financial compensation for its ruinous military effort and France more concerned with defeating Spain. This split gave hope to Vienna and Madrid that they could still win by dividing their enemies.
And so, for 13 years more the armies battled. They marauded over Germany, Bohemia, the Netherlands, Italy, and France, sacking cities and terrorizing populations as they battened off and burned the land. Catholic fought Catholic and Protestant killed Protestant while each murdered, raped, tortured, and burned out the other, spreading famine, pestilence, refugees, cruelty, and death through the heart of Europe. Huge mercenary armies did not so much fight strategic battles as constantly maneuver, plunder, and forage, all the while collecting wages of death. Entire cities were put to the sword out of revenge or reprisal. The conflict left some areas of Germany and Bohemia denuded of half their population, while other provinces paid huge ransoms to approaching armies—of whichever side—to deflect the war elsewhere, escape with their lives, and keep town, livestock, and farms intact. As the war drew to a drawn-out and exhausted close, the armies engaged shrank in size. This was due to the inability of burned and eaten out farms or serially extorted and depopulated towns to sustain relentless demands for contributions to maintain forces on the huge scale seen earlier under Wallenstein and Gustavus. During these last years, given the strength of fortified defenses and the still unsolved problems of mid-17th century logistics, deep cavalry raiding was about the most either side could undertake. And most raids achieved little because of an abiding inability to supply mid-17th century armies on the move and the inherent superiority of fortified defenses.
Henri de la Tour d’Auvergne, Vicomte de Turenne (11 September 1611, Sedan, Ardennes – 27 July 1675)
At Wittstock (October 4, 1636), the Imperial Army lost heavily to the Swedes, so that once more the balance of power swung (as it had in the other direction after Nördlingen) and new hope for victory was raised among the Protestant princes of Europe. In 1638 France and Sweden signed the Treaty of Hamburg (March 15) providing French subsidies to Sweden and foreswearing a separate peace. At Rheinfelden (March 2–3, 1638) a Protestant army under Bernhard von Sachsen-Weimar destroyed a Bavarian army and took Johann von Werth captive. The Swedes followed up with a victory over the Saxons at Chemnitz (April 14, 1638) and occupation of Bohemia. From September 1640 to October 1641, the full Imperial Diet met for the first time since 1613, to work out the negotiating positions of the Empire for any future peace talks. Not every German prince waited: in July 1641, Friedrich Wilhelm (1640– 1688), the new ‘‘Great Elector’’ of Brandenburg, agreed to a ceasefire with Sweden; in January 1642, the Welf dukes of Brunswick also dropped out of the war (Treaty of Goslar). These defections freed Swedish general Lennart Torstensson to invade Moravia and Silesia. A determinative battle was Second Breitenfeld (November 2, 1642) where Torstensson destroyed an Imperial army and Ferdinand III’s hope to avoid major concessions to Sweden in the final settlement. The other important battle of this last phase of the war was Rocroi (May 19, 1643), where the seasoned but sullen and shrunken Army of Flanders was defeated by a French army of 22,000 led by the ‘‘Great Conde´’’ (Louis II). The French suffered a disaster of their own at Tüttlingen (November 24–25, 1643), after which Turenne was recalled from Italy and given command of the shattered Armee´ d’Allemagne.