As 1637 rolled through, it took another major figure of the war with it. Ferdinand II had spent literally his entire tenure as Holy Roman Emperor fighting all comers for the right to rule as he saw fit, and it had killed him. The new Emperor Ferdinand III was just 29, a musician, architect, and pragmatic intellectual. He was out to secure peace and the legacy of the House of Austria, and like Richelieu the religion of his allies mattered less to him than it had for his father. Religious exhaustion was becoming a common theme across the national divides. In the 1640’s, Crown Prince Rupert, son of the Winter King, returned to England to become the dashing Cavalier of King Charles in the English Civil War. Family and nation, it seemed, were the defining sources of pride and conflict for the younger generation.
The cost for this secular awakening had been high. By 1637 Armies on all sides were at least a third smaller than they had been. Sweden’s forces across all of Germany were down to just 45,000 men in spite of their reinforcements. Many garrisons simply surrendered, confident that they could simply sign up for the winning side. Tactics had switched in part by necessity, as it takes a special kind of man who is willing to hold a pike in the face of a charging horseman and most of those were now dead somewhere. Yet even as he pulled men to bundle the Swedes back into Pomerania, Ferdinand only succeeded in showing the allies the value of good teamwork.
In spite of Wittstock, the Imperial forces continued to hold their own, and the Swedes were hard pressed. So pressed, in fact, that Oxenstierna made overtures for peace to the Hapsburgs. After all, from his perspective back in Stockholm, the war had become a near constant drain on the Swedish empire. Even conceding their possible gains in Poland had thus far bought them nothing but more grief and war.
Whether the offers were genuine or not wasn’t clear, but Richelieu was sufficiently rattled both by the invasion of France and the possibility of losing his allies that he offered the concessions the Swedes needed to stay on in the war. The resulting 1638 Treaty of Hamburg was a final and concrete alliance between Sweden and France. Either they were in this for the duration, or neither of them were going to get the kind of gain they had already invested so much blood and treasure pursuing. In exchange for a larger subsidy with no conditions, the Swedes agreed that in war or peace the allies would decide jointly. With the new funds, another 14,000 Swedes and Finns were combed out from the countryside, armed, dressed, and shipped to Germany. The war would go on, and the allies began to more closely plan and coordinate their campaigns.
Along the Rhine near the Swiss border, Bernhard of Saxe-Weimar finally proved his worth and defeated the Imperial army of Johann von Werth. In the battle of Rheinfelden from February 28-March 3 1638, Bernhard was caught with half his army on each bank of the Rhine by Werth, and not only managed to survive the first encounter but subsequently brought his entire force around by another crossing into the rear of the Imperial forces. Capturing the Imperial leadership, Bernhard threw them a banquet in the evening to toast their miserable failure and the swelling of his own army with their defecting soldiers.
Riding high, Bernhard finally moved his ragtag mix of Germans, Swedes, Scots, and Frenchmen against the key fortress of Breisach. Rising sharply above the Rhine on a jut of rock, the fortress controlled the entire region, and was the key to the last viable route of the Spanish Road. As a result, two frantic Imperial efforts were launched to relieve the fortress. Neither worked, and the relief armies were crushed attempting to break the siege lines. By December 19th, the garrison was down to 400 starving men, facing the same long odds that every starving garrison faces. Any living thing that could go into a pot had long since done so. Leather goods had been scraped down and boiled. Most notoriously, Bernhard learned to his horror that some of his soldiers captured in the fighting had been imprisoned in the fortress. The survivors had been forced to eat any prisoners who had starved to death. On the condition that they could march out alive, the garrison finally surrendered Breisach.
While this should have been great news for the French, the celebration in Paris was dampened when Bernhard demanded the dukedom of Alsace on the spot. Like Wallenstein, Bernhard seemed to have ambitions well above his military role, but exactly what ambitions those were is a little ambiguous. It seemed unlikely that Bernhard was out to conjure up a German option that straddled the line between France and the Hapsburgs. Indeed, he had already rejected some quiet overtures from the gelded Protestant leader Johann Georg for just such an option. Yet neither did Bernhard seem to just have personal gain on the brain. Perhaps in the grand tradition of Franco-German relations, he was simply hoping to retain Alsace for Germany’s territory. The situation could have turned dire for France if Bernhard of Saxe-Weimar hadn’t quickly fallen ill and died in 1639. Now under proper French leadership, Bernhard’s army morphed into a royal French force. The last somewhat German Protestant force was effectively abandoned for another foreign power. For five years the Franco-Swedish-Dutch armies and the Hapsburgs had been locked in a death grip with no clear winner. Something had to break under the pressure.
 His efforts in this regard would be regularly derailed by his Spanish cousins, and the conditions they often tagged to the subsidies they offered the imperial crown.