Martin Luther and his colleagues in Wittenberg were not the only theologians to set forth a theological program of reform in the early sixteenth century. In fact, many competing visions of reform emerged. In the early 1520s Ulrich Zwingli led a religious reform in Zurich, one of the cantons of the Swiss Confederacy. While he was not the only early Protestant reformer in Switzerland, Zwingli became the most significant religious leader of the Swiss Reformation until his death in 1531. Zwingli won the support of the government of Zurich that led to significant changes in faith and practice. These included a focus on Holy Scripture as the final authority in religious matters, salvation by grace through faith alone, the rejection of the papal authority, the intercession of saints, monastic orders, clerical celibacy, and purgatory. The dramatic shift became obvious when a new communion service in German replaced the medieval Latin mass. [endnote 1]
A rift between the Wittenberg-based reform movement and Swiss Reformers emerged in 1525. In that year Ulrich Zwingli set forth his teaching on the nature of the Lord’s Supper in various works. His teaching represented a refutation not only of the Roman doctrine of transubstantiation, but a rejection of any belief in the physical presence of Christ’s body and blood in the Lord’s Supper. Appealing to a spiritual, symbolic interpretation of Holy Scripture, Zwingli asserted, “The meaning of Christ’s words becomes perfectly plain to this effect: ‘This feast signifies or is the symbol by which you will recall that my body, mine, the Son of God, your Lord and Master, was given for you.’ ” [endnote 2] Zwingli defended this symbolic interpretation of the Lord’s Supper in various places. Additionally, he asserted that Christ’s body rose to heaven and therefore could not be present in Holy Communion. [endnote 3]
Ulrich Zwingli’s teaching alarmed Luther and his fellow pastors in Germany. Luther had made his position on the Lord’s Supper very clear before he had read Zwingli’s work. In 1523 Luther described the Words of Institution as “…the sum and substance of the whole gospel.” Later in the same work he explicitly rejected a symbolic interpretation of these words by stating, “But we should and will simply stick to the words of Christ—he will not deceive us—and repel this error with no other sword than the fact that Christ does not say: ‘This signifies my body,’ but ‘This is my body.’ ” [endnote 4] Additionally, in January 1525 Luther refuted Andreas Karlstadt’s symbolic teaching of the Lord’s Supper in the second part of Against the Heavenly Prophets in Matters of Images and Sacraments. Luther identified the devil as the source of Karlstadt’s doctrine. After many pages that addressed Karlstadt’s main writings, Luther summarized his position, “…we could say that Dr. Karlstadt robs God of his honor, contradicts the truth, destroys the teaching of St. Paul, and makes the passion of Christ unnecessary, since he denies, in the face of clear and strong texts, that the body and blood of Christ are in the sacrament.” [endnote 5]
When Zwingli’s writings appeared, Luther and his colleagues emphasized the Words of Institution to refute the Swiss theologian’s teaching concerning the Lord’s Supper. In fact, Luther’s fellow reformer and pastor, Johannes Bugenhagen, first wrote specifically against Zwingli in 1525. In the same year, another pastor in southwestern Germany, Johannes Brenz, published a document that agreed with Wittenberg theologians and rejected Ulrich Zwingli’s symbolic teaching. Brenz especially attacked the teachings of Johannes Oecolampadius, a theologian in Basel who agreed with Zwingli. Martin Luther added a preface to a German translation of Brenz’s work in 1526. [endnote 6]
Dr. Luther wrote his first major statement against Zwingli and other promoters of a figurative understanding of the Lord’s Supper in 1526. Although published in October, The Sacrament of the Body and Blood of Christ—Against the Fanatics was an edited version of Luther’s sermons from Holy Week of 1526. While Luther did not mention Zwingli’s name, he clearly warned his congregations and readers against a symbolic understanding of the Eucharistic meal. Luther stated that he would advise someone who did not believe in Christ’s physical presence in the bread and wine to refrain from participation in the Lord’s Supper. He also believed the devil had inspired this false teaching. Luther stated that the controversy revolved around a misunderstanding of the Words of Institution. For example, Luther wrote, “These words are quite clear and explicit: take bread, give thanks, give, bid them eat and drink, this is my body, this is my blood. The fanatics really knock themselves out struggling with these words.” Additionally, Luther observed that Christ’s bodily and bloody presence in the bread and wine was analogous to Christ’s miraculous conception and birth. [endnote 7] In 1527 Luther and Zwingli both published significant works on the Lord’s Supper that represented an expansion of the controversy that culminated in the Marburg Colloquy in 1529. We will discuss those events in Part II.
 On Zwingli’s life and career see Carter Lindberg, The European Reformations (Oxford: Blackwell, 1996), 169-181; and Herman Sasse, This is My Body, Rev. Ed. (Adelaide, Australia: 1977), 92-106.
 Ulrich Zwingli, “Letter to Matthew Alber Concerning the Lord’s Supper,” Trans. H. Wayne Pipkin, Huldrych Zwingli Writings, vol. 2 (Allison Park, PA: Pickwick, 1984), 139.
 Sasse, This is My Body, 112.
 Martin Luther, The Adoration of the Sacrament, Luther’s Works, vol. 36 (Philadelphia: Fortress, 1959), 277, 280-81 [Hereafter LW with volume and page number].
 Martin Luther, LW 40: 144-223 (quote on p. 201). Andreas Karlstadt had been Luther’s colleague in Wittenberg until 1522. On Karlstadt’s relationship to Luther see Martin Brecht, Martin Luther: Shaping the Reformation, 1521-1532, trans. James L. Schaaf (Minneapolis: Fortress, 1990), 157-172.
 Brecht, Shaping the Reformation, 295-297; 303; Sasse, This is My Body, 112-113.
 Martin Luther, The Sacrament of the Body and Blood of Christ—Against the Fanatics, LW 36: 335-346 (quote on pp. 338-339); Brecht, Shaping the Reformation, 306-307.