At first Zwingli regarded Luther as an ally, and union between the followers of Zwingli and Luther may have been possible but for controversies over the Eucharist beginning in 1524. Luther strongly believed it necessary to maintain that Christ is physically present in the Eucharist, while Zwingli along with his followers including John Oecolampadius in Basel favored a symbolic meaning to the rite which would be called sacramentarianism. Martin Bucer in Strasbourg took a mediating position. Luther labeled Zwingli, Oecolapadius, and others who took this view blasphemous, un-Christian, and fanatic. In 1529, German prince Philip of Hesse arranged the Marburg Colloquy as an attempt to reconcile the warring Protestant factions and forge an alliance. The two sides agreed on many points of doctrine but could find no common ground on the Eucharist, and Philip's hope for an alliance failed.