Following the death of his older brother, Philip, in 1131, Louis became heir apparent to the French throne and was crowned as his father's co-ruler.

During his march, as part of the Second Crusade in 1147, Louis stayed at the court of King Géza II of Hungary on the way to Jerusalem.

He and his counsellor, Abbot Suger, pushed for greater centralisation of the state and favoured the development of French Gothic architecture, notably the construction of Notre-Dame de Paris.

Later, Louis supported Henry and Eleanor's sons in their rebellion against their father to foment further disunity in the Angevin realms.

His second marriage to Constance of Castile also produced two daughters, but his third wife, Adela of Champagne, gave birth to a son, Philip Augustus, in 1165.

As a result, he became well learned and exceptionally devout, but his life course changed decisively after the accidental death of his older brother Philip in 1131, when Louis unexpectedly became the heir to the throne of France.

[3][4] He spent much of his youth in Saint-Denis, where he built a friendship with the abbot Suger, an advisor to his father who also served Louis during his early years as king.

[5] In this way, Louis VI sought to add the large, sprawling territory of the duchy of Aquitaine to his family's holdings in France.

In June 1147, in fulfillment of his vow to mount the Second Crusade, Louis and his queen set out from the Basilica of Saint-Denis, first stopping in Metz on the overland route to Syria.

Due to his good relationships with Louis, Géza II asked the French king to be his son Stephen's godfather.

[10] Concerned about the winter shortage of supplies in hostile, Seljuk-held central Anatolia, Louis and Conrad made the decision to alter their journey by 11 November.

[12] In the resulting Battle of Mount Cadmus, the Turks first bombarded the French with arrows and heavy stones, then swarmed down from the mountains and massacred them.

The historian Odo of Deuil gives this account: During the fighting the King Louis lost his small and famous royal guard, but he remained in good heart and nimbly and courageously scaled the side of the mountain by gripping the tree roots [...] The enemy climbed after him, hoping to capture him, and the enemy in the distance continued to fire arrows at him.

But God willed that his cuirass should protect him from the arrows, and to prevent himself from being captured he defended the crag with his bloody sword, cutting off many heads and hands.

[14] Louis decided to leave the Holy Land, despite the protests of Eleanor, who still wanted to help her doomed uncle Raymond, after Easter of 1149.

Departing from Acre, he returned to France via Italy, and after visiting Roger II of Sicily and Pope Eugene III,[15] crossed the Alps and reached Paris in November.

The pretext of kinship was the basis for annulment, but in fact, it owed more to the state of hostility between Louis and Eleanor, with a decreasing likelihood that their marriage would produce a male heir to the throne of France.

The result was a humiliation for the enemies of Henry and Eleanor, who saw their troops routed, their lands ravaged, and their property stolen.

[20] By 1157, Henry II of England began to believe that Louis might never produce a male heir, and that the succession of France would consequently be left in question.

[21] In 1169, Louis was petitioned by the bishop of Le Puy to stop the Viscount of Polignac from attacking travelers through Auvergne.

[22] Louis' reign saw Holy Roman Emperor Frederick I press his claims to Arles, in southeastern France.

More important for English history would be Louis's support for Thomas Becket, Archbishop of Canterbury, whom he tried to reconcile with Henry II.