1. So many events took place in this century that we need to divide it into three parts. So, we will do something different to describe what happened. First, we will give a general overview of everything that took place, and later we will go into detail about each part. This was a very rich century, with figures who changed the history of Christianity, but also full of tragedy and horror.

2 It was in this century that the largest number of crusades in history occurred. It was considered a matter of honor that the tomb of Jesus be recovered, as well as Jerusalem and the entire kingdom of Israel, which were under Muslim control. For this reason, the crusades were organized - military expeditions that departed from Europe, specifically from Rome, toward the Holy Land. According to most historians, there were a total of nine crusades, one of which involved only children.

3 Another type of movement, which could also be called a crusade but did not go to the Middle East, reflected what would later become the Inquisition. It was a kind of crusade focused on persecuting those who thought differently, the so-called heretics.

4 There was the brutal Albigensian Crusade, which persecuted the Cathars in the city of Albi, in southern France. It was initiated by Pope Innocent III to eliminate the Cathar heresy. This crusade was marked by extreme violence, with massacres of entire populations and the burning of Cathars at the stake. From the Church's perspective, the Cathars were heretics.

5 Another persecution carried out by the Church was against the Waldensians. This began in the previous century but reached its peak in this one. The movement was started by a wealthy merchant from Lyon, Pierre de Vou, also known as Peter Waldo.

6 The mendicant orders also emerged, composed of religious men who followed Jesus and took vows of poverty. The Franciscans appeared, led by Francis of Assisi, who aimed to live the Gospel. The Dominicans, led by Dominic of Guzmán, focused on preaching the Gospel and were known as the preachers of Christ.

7 From the Dominicans came an important historical figure, an Italian named Thomas Aquinas. He is considered one of the greatest thinkers of the Catholic Church. He transformed Church history and became a Doctor of the Church. His goal was to unite scientific and religious knowledge during a time of intense conflict and transformation.

8 He sought to show that reason and faith are not contradictory, but complementary. For him, the Church could not remain purely dogmatic; it needed a rational aspect. His thinking was similar to that of the Jewish thinker Ramban and the Muslim philosopher Averroes.

9 Thomas Aquinas wrote the Summa Theologica, the masterpiece of Scholasticism, which synthesizes Catholic doctrine. It is still studied today and includes, among other things, five arguments for the existence of God.

10 This movement, called Scholasticism, brought Christianity into universities. Christianity moved from temples into academic institutions.

11 There is a cathedral in Rome called San Giovanni in Laterano, considered the mother of churches. It was built in the 4th century and later became the seat of the Roman Church. It was eventually replaced by St. Peter's Basilica. According to tradition, Pope Innocent III dreamed of Francis of Assisi supporting this church.

12 Several Lateran Councils were held. In this century, the Fourth Lateran Council established key doctrines. One of them was transubstantiation, which became an unquestionable dogma.

13 Another topic discussed was confession. Catholics were required to confess at least once a year, acknowledging their sins to a priest.

14 Heresies were strongly addressed. In 1231, Pope Gregory IX officially established the Inquisition as a Church tribunal.

15 Initially meant to judge religious crimes, it later became distorted, leading to exploitation, persecution, and executions, often for wealth.

16 Not only heretics were condemned, but also wealthy individuals, whose assets were confiscated before sentencing.

17 The strategies of the crusades evolved. After failing to capture Jerusalem directly, they attempted to control other regions such as Egypt, but were unsuccessful.

18 Crusades also occurred in the Iberian Peninsula, which had been under Muslim control since 711.

19 The Fourth Crusade (1202–1204) diverted to Constantinople, where Western Christians fought Eastern Orthodox Christians.

20 The region briefly returned to Roman Catholic control, but was later reclaimed by the Eastern Church.

21 Around 1212, the Children’s Crusade occurred, based on a literal interpretation of Jesus’ words about children.

22 Two children, Stephen and Nicholas, led this tragic movement.

23 Many children were killed or enslaved. It remains one of the darkest events in history.

24 The crusades had religious, political, economic, and territorial motivations.

25 The Fifth Crusade (1217–1221) targeted Egypt. Francis of Assisi participated.

26 Francis managed to speak with the sultan Al-Kamil, achieving what armies could not, but peace was rejected.

27 The Sixth Crusade (1228–1229), led by Frederick II, achieved diplomatic success, allowing Christian access to holy sites.

28 The Seventh and Eighth Crusades, led by Louis IX of France, ended in failure, and Louis died.

29 Louis IX became a martyr-like figure in Christianity.

30 The Ninth Crusade (1271–1272) failed. In 1291, Acre fell, marking the end of the crusades.

31 Jerusalem remained under Muslim control, and conflicts persist to this day.

32 The crusades intensified hostility between Christians and Muslims, leaving lasting consequences.

33 The House of Wisdom in Baghdad declined due to growing hatred and intolerance.

34 The Albigensian Crusade (1209–1229) targeted Cathars in southern France.

35 The Church opposed the Cathars because they rejected papal authority.

36 They were accused of Manichaeism.

37 They were also labeled Gnostics.

38 They were considered Docetists.

39 The Cathars attracted many followers, which alarmed the Church.

40 Pope Innocent III initially sent missionaries to convert them.

41 When they refused, military crusades massacred them, including civilians.

42 Unlike other crusades, the Cathars were unarmed civilians.

43 Another figure was Peter Waldo, who believed Scripture should be the foundation of faith.

44 He inspired followers, but the Church persecuted them.

45 His movement later influenced the Protestant Reformation