In 1531, war erupted between the Catholic coalition of states and the Protestant states, a fatal chapter in the religious turbulences of the Reformation. Ulrich Zwingli, a most prominent leader of the Swiss Reformation, took part actively in the battle. Famous for his firm Protestant beliefs, Zwingli not only led religious reforms but also led a band of Protestant soldiers personally to fight in the Swiss Civil Wars. The war reached its climax at the Battle of Kappel, a turning point in Swiss history.

In this battle, Zwingli was fatally killed. While commanding his soldiers, he was killed, and the Protestant victory led to an abrupt cessation of his reforms in the region. His assassination did not bring a sudden halt to the war over religion, however. The Battle of Kappel led to the issuing of the Treaty of Kappel, which, although achieving a temporary truce, in effect solidified the religious and political division between Protestant and Catholic states in Switzerland.

This treaty and subsequent era of peace left Switzerland religiously divided for centuries. The Protestant and Catholic areas were engaged in an uneasy standoff, each with their own political and religious structures. The death of Zwingli and the result of the battle served to highlight the wider religious tensions sweeping Europe at the time, with Switzerland as a microcosm of the wider Protestant-Catholic conflict.