The Protestant Reformation made rapid initial gains in both Poland and Hungary. In the century or so that followed the Protestant Reformation, the majority of both countries converted to Protestantism (either Lutheranism or Calvinism); however, both countries were overwhelmed by the Catholic Counter-Reformation, and most of the gains made by Protestants in the sixteenth century were undone in the seventeenth century.

The Hussite Church emerged from the teachings of Jan Hus. Hus preached reform in the century before the beginning of the more widely impactful Protestant Reformation, but his reforming movement may be seen as part of the wider European trend. The Hussites were centered in Bohemia, in the modern day Czech Republic.

Calvinism was the most effective Protestant faith at penetrating Polish society, and it was the dominant religion in the country for several decades at the height of the Protestant Reformation; however, the Catholic Counter-Reformation was wildly successful, and Calvinism survived only in limited numbers.

The Battle of Mohacs was fought between the forces of Hungary and the Ottoman Empire in 1526. It ended in an overwhelming victory for the forces of the Ottoman Empire, which led the people of Hungary to abandon their Catholic faith, because they thought that it no longer offered the protection of God's grace. They took up Protestantism in large numbers and would hold the faith for a century or so until the Catholic Counter-Reformation returned Hungary to Catholicism.

Throughout Europe, but especially in Germany, Poland, and Hungary the most important factor in determining the religious beliefs of a region or group of people was the religious beliefs of the prince or ruler of that region. If the prince embraced Lutheranism, then a large number of the people under his control would also do so.

In the two centuries before the Protestant Reformation began (in 1517), there were still numerous reform movements going on around Europe. One of the most influential and widely known is the Hussite movement initially inspired by Jan Hus and Jerome of Prague. They were both Czech-speaking people living in the region of Central-Eastern Europe called Bohemia. Their reform was centered around rectifying abuses within the church, and their discourse and correspondence is rife with references to the Pope as the "Antichrist." Not surprisingly, given the atmosphere of this time period, they were also both executed for heresy in the early fifteenth century. It is believed that their writings and martyrdom laid the foundations for the swift rise of Protestantism in Bohemia and Poland.

Pogroms were organized attacks on Jewish communities in Russia carried out by the state in the nineteenth and early twentieth centuries.

During the Protestant Reformation, the Ottoman Empire invaded Hungary (then under control of the Hapsburg Holy Roman, and Catholic, Empire). The Ottomans conquered the territory and the Hungarian people lost faith in their Catholic rulers, and in Catholicism itself, to protect them. By 1600, the vast majority of the country had converted to Protestantism, although this would be undone by the Catholic Counter-Reformation.

The ruling family of Poland remained Catholic throughout the Protestant Reformation, but the nobles and landed aristocracy were quick to embrace Protestantism. Interestingly, the peasantry generally sided with the King and with not the nobles and remained fiercely Catholic.

The Lutheran movement was spread initially through the German-speaking princely states of central Europe and was primarily a German-speaking movement throughout. The German-speaking people of Hungary were influenced by the writings of Luther and his German compatriots more than anyone else, and the religion of Lutheranism took off far more swiftly with them. The Lutheran Confession was adopted in Hungary in 1545. The Magyar people of Hungary (people who speak Hungarian) favored the Reformed Church of Switzerland, of Zwinglianism, and they adopted the Helvetic Confession in 1567. A Confession, to help clarify, is an expression of faith or a definition of what the group believes.