These endeavours on the part of his opponents led Zwingli to meditate on plans for leaguing together for the purposes of mutual defence all who had accepted the Reformation. His plans from the first went beyond the Swiss Confederacy.
The imperial city of Constance, the seat of the diocese which claimed ecclesiastical authority over Zurich, had been mightily moved by the preaching of Ambrose Blaarer, and had come over to the Protestant faith. The bishop retired to Meersburg and his chapter to Ueberlingen. The city feared the attack of Austria, and craved protection from the Swiss Protestants. Its alliance was valuable to them, for, along with Lindau, it commanded the whole Lake of Constance. Zurich thereupon asked that Constance be admitted within the Swiss Federation. This was refused by the Federal Diet (Nov. 1527). Zurich then entered into a _Christian Civic League_ (_das christliche Bürgerrecht_) with Constance,--a league based on their common religious beliefs,--promising to defend each other if attacked. The example once set was soon followed, and the two following years saw the League increasing rapidly. Bern joined in June 1528, St. Gallen in Nov. 1528, Biel in January, Mühlhausen in February, Basel in March, and Schaffhausen in October, 1529. Strassburg was admitted in January 1530. Even Hesse and Würtemburg washed to join. Bern and Zurich came to an agreement that Evangelical preaching must be allowed in the Common Lands, and that no one was to be punished for his religious opinions.