Why did Philip organize the Colloquy of Marburg in 1529?

Philip of Hesse organized the Colloquy of Marburg in 1529 primarily to address the political vulnerability of the Protestant movement following the second Diet of Speyer.12

Philip feared that Roman Catholic forces, led by Emperor Charles V, would use military power to suppress the Reformation. To counter this threat, he sought to establish a unified Protestant defensive alliance. However, he recognized that doctrinal divisions—specifically the long-standing disagreement over the Eucharist between Martin Luther and Huldrych Zwingli—prevented the formation of a common confession necessary for such a confederation.123

By convening the colloquy, Philip hoped to reconcile these theological differences through personal discussion, thereby clearing the path for a cohesive political and military front against the House of Habsburg.123