Martin Luther's mind was unshakably fixed as he sat in the great hall of the medieval castle in Marburg, Germany, on the morning of October 2, 1529.

He had come to Marburg grudgingly, at the request of the Protestant Landgrave of the German state, Philip of Hesse, who had summoned Luther and other leading German and Swiss reformers to a meeting ostensibly of great theological importance. But the real impetus for the gathering was strictly political. That underlying fact made the outcome of this "Marburg Colloquy" a foregone conclusion.

To Luther, theological truth could never be allowed to take a back seat to political expedience. Indeed, if Luther had not had matters of greater concern on his mind as more than 50 of the most influential Protestant reformers in Europe met for this first day of public discussion, he might have appreciated the irony of the setting Philip had chosen—the foundations of the gothic hilltop fortress, much like his own convictions, were firmly set in stone, and could not be moved.

Whether religious or political, the Marburg Colloquy undeniably represented a watershed in the course of the Reformation, and Europe's Protestant princes had good reason to fear that its failure could doom the movement. Religion and politics of the sixteenth century co-mingled to a greater degree than Luther wanted to admit, and not everyone shared his scruples against manipulating one in order to influence the other.

The most immediate example of this, and the direct cause for the colloquy, was the resolution drafted by the second diet of Speyer, which had convened in April 1529. The resolution aligned the Holy Roman Empire firmly behind the Catholic Church in opposition to the reformers, thereby threatening them with effective suppression.

Communion as dis-union

Philip recognized the need for the disunited reformers in Hesse, Saxony, Strasbourg, Zurich, and Basel to form a common front based on a reformed theology on which all could agree. The chief obstacle, everyone knew, would be the divide over the Eucharist, the Sacrament of the Lord's Supper.

Luther and Ulrich Zwingli stood far apart in their interpretations, and between them lay a great chasm, which neither, it seemed, could cross over.

Zwingli, the chief spokesman for the Swiss reformers, held firmly to the belief that the bread and wine offered through the Sacrament are symbolic of Christ's sacrifice and thus merely the outward signs by which the recipients acknowledge the grace that they have already received.

Luther vehemently insisted that Christ is literally present in the communion elements, which are the means by which grace is imparted to the faithful. The German reformer's position more closely resembled the Catholic doctrine than it did the Swiss, a point that earned him no little scorn from the more radical Protestants.

Philip had expended great energy just to persuade Luther to come to Marburg, and his presence in Marburg Castle must have been deemed a harbinger of good things to come.

But while for the next two days Luther and Zwingli drew close enough to look each other in the eye and launch invectives back and forth across a narrow table, the theological gulf between them remained unbridged.

Indeed, following a day of private consultations on October 1, Luther surely knew what the others only feared: as the public portion of the proceedings opened on October 2, the colloquy was not just beginning, it had for all practical purposes already ended. No compromise would emerge from this summit.

"You're being obnoxious"

Philip's chancellor opened the public discussion with an admonition to both parties to "[settle] the dispute over the Lord's Supper … in a spirit of moderation."

Luther's response left little reason to expect such results: "Noble prince," he replied. "Undoubtedly this colloquy is well intentioned … although I have no intention of changing my mind, which is firmly made up." As he spoke, Luther wrote on the table in chalk: "This is my body." Then he covered the quote from the Gospel of Matthew with a velvet cloth, and insisted that the Swiss reformers prove from Scripture that Christ's body is not physically present in the communion elements.

Zwingli and his supporters accepted the challenge, quoting the Gospel of John to support their own interpretation. Luther's reaction clearly demonstrated his unwillingness to engage in a meaningful debate. "You're being obnoxious," he countered.

Zwingli patiently tried to draw Luther into a more substantive discussion, calling his attention once more to John's Gospel. "You're trying to dominate things," Luther countered. "It serves no purpose."

Again Zwingli quoted John. "You're in Hesse, not Switzerland," Luther answered, refusing even to acknowledge Zwingli's reference to Scripture.

The "debate" progressed no further. In an effort to make a show of unity, Philip asked Luther to draft a statement of Christian doctrines on which all concerned could agree. The resulting 15 "Articles of Marburg" set out the German and Swiss reformers' agreement on such doctrines as original sin, atonement, the Incarnation, and baptism. Since none of these had ever really been disputed—indeed they had never been mentioned during the colloquy—the document did not reflect any real progress of the sort Philip had desired.

Better blood than wine

The verdict of history has been that at Marburg Luther missed the last best chance to unite the factious Protestants into a universal reformed church.

But such a judgment presumes that compromise represented a greater good than spiritual integrity. Luther himself would have vehemently disagreed.

In fact, in a cynical way Luther probably considered the colloquy a rousing success, precisely because religious conviction had not caved in to political necessity. If truth must bow to expediency, he surely would have argued, he might just as easily appease the Pope as Zwingli and Philip of Hesse. ("I would rather drink blood with the Pope, than mere wine with the Swiss," he observed caustically.)

In the long run, Reformation theology left Luther behind, and if the Marburg Colloquy were reconvened today, few would now side with his view.

But in another sense, events proved Luther was right: disagreement over the Lord's Supper was not fatal to the reform movement, and by resisting the temptation to value convenience more than conviction, he may in fact have reinforced the Protestant ethos—in all its varied forms.

Bruce Heydt is managing editor of British Heritage magazine.