Many Germans remained neutral, viewing it as an inheritance dispute within the Holy Roman Empire, and Emperor Ferdinand quickly suppressed the Bohemian Revolt.

[5] Expectations of widespread support proved unrealistic; by the end of 1630, the only new Swedish ally was the Imperial town of Magdeburg, then besieged by the Catholic League.

[7] Although the Swedes expelled the Imperials, this simply replaced one set of plunderers with another; Gustavus could not support so large an army, and his unpaid and unfed troops became increasingly mutinous and ill-disciplined.

[7] In January 1631, John George of Saxony hosted a conference of German Protestant states at Leipzig, hoping to create a neutrality pact.

Hoping to use Sweden to occupy Spanish forces in Germany, in 1629 Richelieu appointed Hercule de Charnacé French envoy in the Baltic region, with responsibility for negotiating a deal with Gustavus.

Talks progressed slowly; de Charnacé quickly concluded the Swedish monarch was too powerful a character to be easily controlled and urged caution.

[9] The (13 October) 1630 Treaty of Ratisbonne concluded the Mantuan War in France's favour but in return, French negotiators undertook not to agree alliances with members of the Holy Roman Empire without Ferdinand's approval.

[10] Doing so would undermine the entire basis of French foreign policy; Louis XIII refused to ratify the deal, leading to an internal power struggle between Richelieu and the Queen Mother, Marie de Medici.

De Charnacé was instructed to agree a treaty as soon as possible; after discussions with the Swedish diplomats, Gustav Horn and Johan Banér, it was signed at Bärwalde on 23 January 1631.

Gustavus embarked on a series of stunning military victories, and Protestant retribution for Magdeburg became a considerable embarrassment for Richelieu, a Cardinal of the Catholic Church.

[12] The poorly worded Bärwalde treaty gave Gustavus a great deal of freedom, while Magdeburg brought him support from the Dutch and England among others.