Wolfgang Capito in the context of "Protestant reformer"

Martin Bucer (/ˈbuːsər/; Early German: Martin Butzer; 11 November 1491– 28 February 1551) was a German Protestant reformer based in Strasbourg who influenced Lutheran, Anglican doctrines and practices as well as Reformed Theology. Bucer was originally a member of the Dominican Order, but after meeting and being influenced by Martin Luther in 1518 he arranged for his monastic vows to be annulled. He then began to work for the Reformation, with the support of Franz von Sickingen.

Bucer's efforts to reform the church in Wissembourg resulted in his excommunication from the Catholic Church, and he was forced to flee to Strasbourg. There he joined a team of reformers which included Matthew Zell, Wolfgang Capito, and Caspar Hedio. He acted as a mediator between the two leading reformers, Martin Luther and Huldrych Zwingli, who differed on the doctrine of the Eucharist. Later, Bucer sought agreement on common articles of faith such as the Tetrapolitan Confession and the Wittenberg Concord, working closely with Philipp Melanchthon on the latter.

The Tetrapolitan Confession (Latin: Confessio Tetrapolitana, German: Vierstädtebekenntnis), also called the Strasbourg Confession or Swabian Confession, was an early Protestant confession of faith drawn up by Martin Bucer and Wolfgang Capito and presented to the Emperor Charles V at the Diet of Augsburg on 9 July 1530 on behalf of the four south German cities of Konstanz, Lindau, Memmingen and Strasbourg. (The name "Tetrapolitan" means "of the four cities".) The confession was based on an early draft of the Augsburg Confession to which Bucer and Capito had secretly obtained access, but amended in the direction of Zwinglianism. Its purpose was to prevent a schism within Protestantism. It is the oldest confession of the Reformed tradition produced in Germany.

Bucer and Capito were called to the Diet of Augsburg by the envoys of Strasbourg, who were aware that Philipp Melanchthon was working on a Saxon Confession that would represent the Lutheran position. The north Germans (Lutherans) and the south Germans and Swiss had been divided in opinion since 1524 on the subject of the Lord's Supper, with the Lutherans supporting sacramental union (the physical presence of Christ's body in the sacrament) and the Zwinglians memorialism (the sacrament as a spiritual memorial only). This division had reached its high point in the Marburg Colloquy between Zwingli and Luther in 1529.