Anti-Catholic posters appear in Paris and other cities supporting Huldrych Zwingli's position on the Mass.

The Affair of the Placards was an incident in which anti-Catholic posters appeared in public places in Paris and in four major provincial cities, Blois, Rouen, Tours and Orléans, in the night of the 17 to 18 October 1534. One of the posters was posted on the bedchamber door of King Francis I at Amboise, an affront and a breach of security that left him shaken. The Affaire des Placards brought an end to the conciliatory policies of Francis, which had formerly attempted to protect the Protestants from the more extreme measures of the Parlement de Paris, and also of the public entreaties for moderation of Philip Melanchthon.

Huldrych or Ulrich Zwingli was a Swiss Christian theologian, musician, and leader of the Reformation in Switzerland. Born during a time of emerging Swiss patriotism and increasing criticism of the Swiss mercenary system, he attended the University of Vienna and the University of Basel, a scholarly center of Renaissance humanism. He continued his studies while he served as a pastor in Glarus and later in Einsiedeln, where he was influenced by the writings of Erasmus. During his tenures at Basel and Einsiedeln, Zwingli began to familiarize himself with many criticisms Christian institutions were facing regarding their reform guidance and garnered scripture which aimed to address such criticisms.