Bertrand, the eldest son of Raymond IV of Toulouse, has ruled Toulouse since Raymond left on the First Crusade in 1095—although, between 1098 and 1100, had been dispossessed by his cousin Philippa and her husband Duke William IX of Aquitaine, who had marched into Toulouse and captured it, before mortgaging it back to Bertrand in 1100 to fund Duke William's expedition to the Holy Land.

Bertrand, the eldest son of the Raymond IV, has been ruling Toulouse in his absence.

After Raymond's death, the Barons of Toulouse had chosen Raymond’s six-year-old son Alfonso-Jordan to replace Bertrand, who, thus overthrown, has traveled to the east with fresh Genoan, Pisan and Provençal troops, arriving at Mons Peregrinus in 1108 to claim it for himself.

Here, he quarrels with the regent, William-Jordan, over the inheritance of the Raymond's lordship, and over the regency of still-unconquered Tripoli.

William allies himself with Tancred, Prince of Galilee, Regent of the Principality of Antioch, while Bertrand asks Baldwin I of Jerusalem to intervene.

Baldwin I, Baldwin of Bourcq, and Joscelin of Courtenay allied with Bertrand and William and Tancred were forced to compromise.

The Franks gather in force outside Tripoli in 1109.

Besieged for the past seven year and partially destroyed, Tripoli waits in vain for reinforcements from Fatimid Egypt.

A compromise decided in the course of a dispute beneath the walls of the city, and arbitrated by Baldwin of Jerusalem, allows the city to be captured: the County of Tripoli will be divided between the two claimants, William-Jordan, as a vassal of the Principality of Antioch, and Bertrand, as a vassal of Jerusalem.

The city falls on July 12, and is sacked by the crusaders.

One hundred thousand volumes of the Dar-em-Ilm library are deemed "impious" and burned.

The Egyptian fleet arrives eight hours too late.

Most of the inhabitants are enslaved, the others are deprived of their possessions and expelled.

A short time later William dies of an arrow wound sustained during the siege, and the county passes to Bertrand alone.

Tripoli joins the Kingdom of Jerusalem, and the Principality of Antioch and the County of Edessa as a fourth crusader state; unexpectedly defeated by an army under Shahriyar and his son Qarin III

…the Crusaders also capture Beirut.

Bertrand of Toulouse, ruling in Tripoli until his death in 1112, is succeeded by his son Pons in Tripoli, and by his brother Alphonse-Jordan in Toulouse—although Toulouse is at this point again lost to his cousin Philippa and her husband Duke William IX of Aquitaine.