A coalition of Protestant German states from the Protestant Union or League of Evangelical Union (also known as the Evangelical Union or Union of Auhausen), to defend the rights, lands and person of each member following the establishment, by the Holy Roman Emperor and Duke Maximilian I of Bavaria, of Roman Catholicism in Donauwörth in 1607 and after a majority of the Reichstag have decided in 1608 that the renewal of the Peace of Augsburg of 1555 should be conditional upon the restoration of all church land appropriated since 1552.

Meeting on May 14, 1608, in Auhausen, near Nördlingen, the Protestant princes of the Palatinate, Anhalt, Neuburg, Württemberg, Baden, Ansbach, Bayreuth, Hesse-Kassel (or Hesse-Cassel), Brandenburg, Ulm, Strasbourg and Nürnberg form a military league under the leadership of Frederick IV of the Palatinate.

The Protestant Union is weakened from the start by the non-participation of several powerful Protestant rulers, such as the Elector of Saxony.

The Union is also beset by internal strife between its Lutheran and Calvinist members.

The union of Protestant princes, formed at the beginning of the dispute over the duchies of the late and childless duke of Jülich-Cleves-Berg, still lacks several powerful Protestant rulers, such as the Elector of Saxony.

The conduct of the Union in the Jülich dispute and the warlike operations of the Union army in Alsace appear to make inevitable a battle between the Union and ...

...the military league of important Catholic states formed in response.

When Austria and Salzburg finally join in 1613, at Ratisbon, the assembly now appoints no less than three war-directors: Duke Maximilian, and Archdukes Albert and Maximilian of Austria.

The object of the League is now declared "a Christian legal defense."

The Hohenzollerns of Brandenburg have sought to expand their power base from their relatively meager possessions, although this brought them into conflict with neighboring states.

After John William, Duke of Julich-Cleves-Berg, died childless in 1609. his eldest niece, Anna, Duchess of Prussia, the wife of John Sigismund, Elector of Brandenburg, had promptly claimed the inheritance; Brandenburg had sent troops to take hold of some of John William's holdings in the Rhineland.

Unfortunately for John Sigismund, this effort will become tied up with the Thirty Years' War and the disputed succession of Julich.

The cities of Cleves, Mark, Jülich, Berg, and Ravensburg, after the month-long War of the Jülich Succession, had rejected the Dortmund Recess since the accord had been developed without the consent of all five cities.

Overall, the five cities prefer to be represented by one prince rather than two.

The Dortmund Recess is ultimately replaced by the Treaty of Xanten, signed on November 14, 1614, and ending the Julich-Cleves War, today recognized as a precursor to the Thirty Years' War.

Palatinate-Neuburg takes the duchies of ...

...Jülich and ...

...Cleves and ...

...the County of Mark.

The membership of Austria makes the Catholic League part of the struggles between the emperor and his Protestant vassals in Bohemia and Lower Austria, which will lead to the beginning of the Thirty Years War.

Duke Maximilian of Bavaria refuses to accept the resolutions of Ratisbon and even resigns the post as president, when Archduke Maximilian of Austria, the Prince Elector of Mainz, and the Prince Elector of Trier, protest the inclusion of the Bishop of Augsburg and the Provost of Ellwangen in the Bavarian Directory.

Bavaria, with the Prince-Bishops of Bamberg, Eichstädt, Würzburg, and the Prince-Provost of Ellwangen, form a separate league on May 27, 1617; it is to last for nine years.