Gilbert is principally remembered for his militancy related to the
Crusader invasion of Egypt, and he encouraged Amalric of Jerusalem to declare war on Egypt in order to expand territories of the kingdom. In the summer of 1164, a Frankish army accompanied by large contingents of
Templars and Hospitallers led by Bohemond III of Antioch, Raymond III of Tripoli,
Joscelin III of Edessa,
Hugh VIII Lusignan and
Constantine Kalamanos, Byzantine governor of
Cilicia, was deployed. On 12 August 1164, this force was defeated at the
Battle of Harim by
Nur ad-Din, ruler of the
Zengid dynasty. The latter pushed his advantage by taking the city of
Banias on October 18, 1164, key to the passage between
Tyre and
Damascus. Nur ad-Din late agreed to a treaty on the basis of half-sharing with the Christian troops of the territory of
Tiberias. In 1167,
Shirkuh, governor of Egypt, deposed by the usurper
Shawar, received permission from Nur ad-Din to reconquer Egypt. He gathered an army in Syria and came to set up his camp at
Giza, opposite Cairo. Amalric learned of this and wanted to cut the road to Shirkuh, but arrived too late, and withdrew to
Ascalon to complete his army, including the Hospitallers. On 30 January 1167, he headed for
Bilbeis, via
Gaza and
el-Arich. Shawar, sensing the danger, allied with Amalric and allowed the Christian troops to enter Cairo. On 18 March 18, they were defeated at the
Battle of al-Babein, and returned to Cairo. They then besieged
Alexandria. After 75 days of siege, Shirkuh sued for peace. He left the land to Shawar, returned to Syria with his army providing the Christians, a significant financial compensation. Gilbert, still convinced that the conquest of Egypt would be a good thing, provided in October 1168 one thousand knights and
Turcopoles to the army. In exchange he asked to own Bilbeis and a vast territory between Syria and the sea. Amalric set out at the end of October, without waiting for the reinforcements promised by
Manuel I Komnenos. On November 4, he seized Bilbeis and on November 13 he was neared Cairo. The Egyptians were determined to defend themselves and Nur ad-Din, Shirkuh and Shawar made an alliance. Amalric's fleet after taking
Tinnis could not go up the Nile and was ordered to withdraw. Amalric offered Shawar a withdrawal in exchange for a large tribute of a million besants, but the approach of Shirkuh forces him to lower his demands by half. On 2 January 1169, the troops of Jerusalem withdrew from Cairo. Amalric decided to send an embassy to the West made up of the Archbishop of Tyre,
Frederick de la Roche, the Bishop of Banias, and Guy de Mauny, the Grand Commander of the Hospitallers, to ask for assistance. In July 1169, the embassy was at the papal court of
Alexander III, in September and November, at the court of
Louis VII of France and then at the court of
Henry II of England. After two years of absence, the embassy returned to Jerusalem empty handed. In the fall of 1169, Amalric, with the help of Manuel I Komnenos and the Hospitallers, began his fourth campaign against Egypt. There again a financial treaty was made with the Hospitallers, with Bilbeis and the adjacent territory promised. The objective was
Damietta, with the Greek and Frankish fleets laying siege by sea and by land at the end of October. But the expedition failed once more, and returned to Tyre on 7 December 1169. ==Retirement and death==