Swabian League

The Swabian League (Schwäbischer Bund) was a mutual defence and peace keeping association of Imperial Estates - Free Imperial cities, prelates, principalities and knights - principally in the territory of the Early medieval stem duchy of Swabia, established in 1488 at the behest of Emperor Frederick III of Habsburg and supported as well by Bertold von Henneberg-Römhild, archbishop of Mainz, whose conciliar rather than monarchic view of the Reich often put him at odds with Frederick's successor Maximilian. The Swabian League cooperated towards the keeping of the imperial peace and at least in the beginning curbing the expansionist Bavarian dukes from the House of Wittelsbach and the revolutionary threat from the south in the form of the Swiss. The League held regular meetings, supported tribunals and maintained a unified force of 12,000 infantrymen and 1200 cavalry.

On 14 February 1488 a new Swabian League was formed, at the Reichstag of Esslingen, not only of 22 Imperial cities but also of the Swabian knights' League of St. George's Shield, bishops, and princes (Ansbach, Baden, Bavaria, Bayreuth, Hesse, Mainz, the Electorate of the Palatinate, Trier, Tyrol, and Württemberg). The league was governed by a federal council of three colleges of princes, cities, and knights calling upon an army of 13,000 men. It aided in the rescue of the future emperor Maximilian I, son of Emperor Frederick III, held prisoner in the Low Countries, and later was his main support in southern Germany.

...
Wikipedia