 Complete the following phrase:  The Danish campaign plan involved three armies; the main force under Christian IV was to advance down the Weser, while Mansfeld attacked Wallenstein in Magdeburg and Christian of Brunswick linked up with the Calvinist 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 