Bernard of Clairvaux, O.Cist (1090 – August 20, 1153) was a French abbot and the primary builder of the reforming Cistercian order.

After the death of his mother, Bernard sought admission into the Cistercian order.

"Three years later, he was sent to found a new abbey at an isolated clearing in a glen known as the Val d'Absinthe, about 15 km southeast of Bar-sur-Aube.

According to tradition, Bernard founded the monastery on 25 June 1115, naming it Claire Vallée, which evolved into Clairvaux.

There Bernard would preach an immediate faith, in which the intercessor was the Virgin Mary.

In the year 1128, Bernard assisted at the Council of Troyes, at which he traced the outlines of the Rule of the Knights Templar, who soon became the ideal of Christian nobility.

On the death of Pope Honorius II a schism breaks out in the Church.

Louis VI of France convenes a national council of the French bishops at Étampes in 1130, and Bernard is chosen to judge between the rivals for pope.

After the council of Étampes, Bernard goes to speak with the King of England, Henry I, Beauclerc, about the king's reservations regarding Pope Innocent II.

Beauclerc is sceptikal because most of the bishops of England support Anacletus II; he convinces him to support Innocent.

Germany has decided to support Innocent through Norbert of Xanten, who s a friend of Bernard's.

However, Innocent insists on Bernard's company when he meetswith Lothair III of Germany.

Lothair becomes Innocent's strongest ally among the nobility.

Despite the councils of Étampes, Wurzburg, Clermont, and Rheims all supporting Innocent, there are still large portions of the Christian world supporting Anacletus.

At the end of 1131, the kingdoms of France, England, Germany, Castile, and Aragon support Innocent; however, most of Italy, southern France, and Sicily, with the patriarchs of Constantinople, Antioch, and Jerusalem, support Anacletus.

Bernard sets out to convince these other regions to rally behind Innocent.

The first person whom he goes to is Gerard of Angoulême.

He proceeds to write a letter known as Letter 126.

This letter questions Gerard's reasons for supporting Anacletus.

Bernard will later comment that Gerard was his most formidable opponent during the whole schism.

After convincing Gerard, Bernard travels to visit the Count of Poitiers.

He is the hardest for Bernard to convince.

He does not pledge allegiance to Innocent until 1135.

After that, Bernard spends most of his time in Italy convincing the Italians to pledge allegiance to Innocent.

He travel to Sicily in 1137 to convince the king of Sicily to follow Innocent.

The whole conflict ends when Anacletus dies on January 25, 1138.

In 1139, Bernard assists at the Second Council of the Lateran.

Bernard denounces the teachings of Peter Abelard to the pope, who calls a council at Sens in 1141 to settle the matter.

Bernard soon sees one of his disciples elected as Pope Eugenius III.

Having previously helped end the schism within the church, Bernard is now called upon to combat heresy.

In June 1145, Bernard travels in southern France and his preaching there helps strengthen support against heresy.

Following the Christian defeat at the Siege of Edessa, the pope commissions Bernard to preach the Second Crusade.

The last years of Bernard's life are saddened by the failure of the crusaders, the entire responsibility for which is thrown upon him.

Bernard dies at age 63, after 40 years spent in the cloister.

He is the first Cistercian placed on the calendar of saints, and is canonized by Pope Alexander III on 18 January 1174.

In 1830, Pope Pius VIII bestows upon Bernard the title "Doctor of the Church".