May 1625, the Lower Saxony kreis elected Christian their military commander, although not without resistance; Saxony and Brandenburg viewed Denmark and Sweden as competitors, and wanted to avoid either becoming involved in the Empire. Attempts to negotiate a peaceful solution failed as the conflict in Germany became part of the wider struggle between France and their Habsburg rivals in Spain and Austria. In the June 1624 Treaty of Compiègne, France had agreed to subsidise the Dutch war against Spain for a minimum of three years, while in the December 1625 Treaty of The Hague, the Dutch and English agreed to finance Danish intervention in the Empire. Hoping to create a wider coalition against Ferdinand, the Dutch invited France, Sweden, Savoy, and the Republic of Venice to join, but it was overtaken by events. In early 1626, Cardinal Richelieu, main architect of the alliance, faced a new Huguenot rebellion at home and in the March Treaty of Monzón, France withdrew from Northern Italy, re-opening the Spanish Road. Dutch and English subsidies enabled Christian to devise an ambitious three part campaign plan; while he led the main force down the Weser, Mansfeld would attack Wallenstein in Magdeburg, supported by forces led by Christian of Brunswick and Maurice of Hesse-Kassel. The advance quickly fell apart; Mansfeld was defeated at Dessau Bridge in April, and when Maurice refused to support him, Christian of Brunswick fell back on Wolfenbüttel, where he died of disease shortly after. The Danes were comprehensively beaten at Lutter in August, and Mansfeld's army dissolved following his death in November. Many of Christian's German allies, such as Hesse-Kassel and Saxony, had little interest in replacing Imperial domination for Danish, while few of the subsidies agreed in the Treaty of the Hague were ever paid. Charles I of England allowed Christian to recruit up to 9,000 Scottish mercenaries, but they took time to arrive, and while able to slow Wallenstein's advance were insufficient to stop him. By the end of 1627, Wallenstein occupied Mecklenburg, Pomerania, and Jutland, and began making plans to construct a fleet capable of challenging Danish control of the Baltic. He was supported by Spain, for whom it provided an opportunity to open another front against the Dutch. On 13 May 1628, his deputy von Arnim besieged Stralsund, the only port with large enough shipbuilding facilities, but this brought Sweden into the war. King Gustavus Adolphus despatched several thousand