During the time of political dissension called the Western Schism, philosophical dissension arose in England in the person of John Wyclif. Wyclif received his Doctorate of Theology in 1372 from Oxford University and later became a professor there. Wyclif was a prolific writer, publishing his first book, Of Logic, in 1360. His early books mostly related to science and metaphysics. In 1377, however, he publishes On Civil Dominion in which he attacks the wealth and power of the church, which is condemned by Pope Gregory XI. He is protected from prosecution by the church by John of Gaunt, Duke of Lancaster, to whom he is clerical advisor.

As the church devotes its energies to solving the Western Schism, Wyclif expands his views, openly preaching his new doctrines. In 1378 or 1379, he publishes On the Church in which he promotes the supremacy of King over church in temporal matters. He also begins preaching that men can communicate directly with God, without the intervention of the church, and calls for a return to the teaching of the Scriptures as the basis of religion. He challenges the doctrine of transubstantiation in the book On the Eucharist in 1380, and publishes his last book On Apostasy later that year. He then retires to his home in rural England and dies on December 31, 1384.

But Wyclif's ideas do not die with him. His books are distributed throughout Europe, but find the most fertile soil in Bohemia, which is ruled by Wenceslas IV, King of Bohemia who is was also elected Holy Roman Emperor in 1378, the same year the Western Schism started. The Bohemian church preaches Wyclif's ideas openly, under the leadership of John Hus, the rector of the University of Prague. Hus is tried and executed for his heresy at the Council of Constance, along with his associate, Jerome of Prague, despite a guarantee of passage from Sigismund, the Holy Roman Emperor.

Like Wyclif, however, Hus' church did not die with him. In Prague, outraged by Hus' betrayal, 452 Bohemian nobles formed the Ultraquist party and covenanted to uphold the teachings of Hus. When Wenceslas IV appointed a new town council in Prague, the Ultraquist marched through downtown in protest. Rocks were thrown from the town hall on the marchers, who then proceeded to storm the building and throw the new town council members out the window to certain death in the crowd below. Upon hearing of this act of defiance, Wenceslas IV had an apoplectice stroke and died. His brother, Sigismund, who was already Margrave of Brandenburg, King of Hungary, and Holy Roman Emperor. He vowed to drown every Hussite heretice in Bohemia.

Martin V also responded to the takeover of Prague by the Ultraquists by calling on a crusade to crush the heretics. In Bohemia, however, another party had formed, the Taborites, who are even more committed to Hussism. The Taborites form an army under John Zizka, which proved repeatedly victorious. The Taborites defeated the crusading armies at Sudomer on March 25, 1420 and on the hill of Vitkov outside of Prague on July 14, 1420. At the mere mention of the arrival of the Taborites in the crusade of 1421, the army dispersed in fear. The Taborites also defeat the armies of Sigismund Oct 31, 1420 at Vysehrad. The Taborites also fought the royalists in Bohemia, defeating them at Kutna Hora on April 25, 1422.

In the interim, the chuch leaders set out the Four Articles of Prague, the charter of the new Hussite church:

I. That the Word of God shall be freely and without hindrance proclaimed and preached by Christian priests in the kingdom of Bohemia.

II. That the Holy Sacrament of the Body and Blood of Christ under the two kinds of bread and wine, shall be freely dispensed to all true Christians who are not shut off by mortal sin.

III. That since many priests and monks held many earthly possessions, against Christ's command and to the disadvantage of their spritual office, and also of the temporal estates, such priests shall be deprived of this illegal power and shall live model lives according to Holy Scripture, and following the way of Christ and the Apostles.

IV. That all mortal sins, and especially those that are public, as also other disorders contrary to the divine law, shall be prohibited and punished by those whose office it is, and that so the evil and false repute to this country may be removed and the well-being of the kingdom and of the Bohemian nation may be promoted.

The Bohemian Diet adopts the four principles in June of 1420, and also moves against the more extremist elements in Bohemia. To aid in the establishment of order, they invite Witold of Lithuania to take the Bohemian throne.Witold instead sends his nephew, Sigismund Korybut, who reigns until early 1423, when he is recalled to Cracow.

Sigismund of Luxembourg is enraged with the appointment of Korybut as governor of Bohemia and hires an Italian mercenary, Pipo of Ozora to ravage Moravia in retaliation. The Taborites, however, defeat Pipo at Nemecky Brod on January 10, 1422. The advance of Frederick, elector of Brandenburg in the fall of 1422 also fails to penetrate Bohemia.

In 1424, a new party is formed from the more extremist Taborites. These are called the Horebites or "Orphans". Dissensions weaken the Hussites, as they aslo lose their general. John Zizka dies on October 11, 1424. He is succeeded by a warrior priest, Prokop. After the German defeat at Usti on June 16, 1426, Prokop goes where no Hussite has gone before, he invades Germany to force recognition of the government in Prague. The Germans instead attack the next year, but are defeated at Stribro. Prokop then overruns Silesia in 1428.

Martin V dies in Febraury of 1431, after investing another crusade against the Hussites. The leader of this crusade, Cardinal Julian Cesarini, marshalls the German forces and again invades Bohemia where they are defeated at Tachov on August 14, 1431. Martin V's successor, Pope Eugene IV decides to compromise and calls the Council of Basel to negotiate with the Hussites. There is only one hitch that occurs in the negotiations. The Hussites press for two kinds of communion, but the representatives of Plzen, which is in the hands of the catholic party, refuses to support the other Bohemians. The Taborites and Orphans, in response, lay siege to Plzen in July 1433. The moderate Ultraquists then take control of the Diet in early 1434, and ally themselves with the minority Catholics. An army is formed to relieve Plzen, and it meets the Taborite/Orphan army at Lippany. The Taborite/Orphan army is destroyed.

On July 5, 1436, the Bohemian delegation accepts the "Compactata" offered at the council, which are markedly similar to the four principles adopted by the Bohemian Diet 16 years earlier:

I. The Holy Sacrament is to be given freely in both kinds to all Christians in Bohemia and Moravia, and to those elsewhere who adhere to the faith of those countries

II. All mortal sins shall be punished and extirpated by those whose office it is to do so

III. The Word of the Lord is to be freely and truthfully preached by the priests of the Lord and by worthy deacons

IV. The priests in the time of the law shall claim ownership of no worldy possessions

Thus, Hussism is accepted as a religion in Bohemia. The Ultraqusts persist as a body until the end of the 16th century, well after the rise of Lutheranism and the other Protestant churches. One branch of Hussism, the so-called "Moravian Brethren" still exist today.