Von Wied & Bucer

[Hermann von Wied, Archbishop of Cologne] went so far as to incorporate Protestants into his reforming efforts: “in 1539 von Wied invited Melanchthon and Martin Bucer to help him in preparing a more thoroughgoing scheme of reform for his diocese, and although Melanchthon eventually refused to compromise himself in this way, Bucer accepted. Similarly, in the same year, Bucer joined with Georg Witzel, a married priest whose early enthusiasm for Luther had cooled and who had returned to Roman obedience, in drafting a Church structure for Ducal Saxony in the wake of the death of Luther’s instransigent enemy Duke Georg.”

It was a remarkable sight: “an Archbishop of the Western Church who openly regretted the failure of repeated efforts to reform the Church, while still proclaiming his loyalty to the Holy See.”

Source: Diarmaid MacCulloch - "Europe's House Divided", as quoted by Peter Leithart, "Ecumenism in the Sixteenth Century", First Things, 6 Feb 2017, https://www.firstthings.com/blogs/leithart/2017/02/ecumenism-in-the-sixteenth-century