Guillaume de Chartres was born in 1178, the son of Milo IV, Count of Bar-sur-Seine, in Champagne, France. Guillaume joined the Order of the Knights Templar, aged sixteen at the Preceptory of Sours, near Chartres.
With the death of Philippe de Plessis in 1209, Guillaume was elected as the 14th Grand Master of the Order of the Knights Templar in 1210. His first official act as Grand Master, was to assist in the crowning of Jean de Brienne as King of Jerusalem. This was just an honorific title for de Brienne, as Saladin had controlled Jerusalem since 1187.
During his reign, Templars flourished in Spain, with victories over the Moors. Spain was like France, with Lords and Noblemen, joining the Templar Order, and donating lands to them.
In 1217, Jean de Brienne (King of Jerusalem), Pelage (Pontifical Legate) and Andre II (king of Hungary) decided to invade Egypt by sea, starting at Damiette (NE side of the Nile Delta). Guillaume de Chartres spoke out against this, but was obliged to follow this conquest. The siege lasted some eighteen months, and all assaults failed. Conflicts between Jean de Brienne the King of Jerusalem and Pelage the Pontifical Lagate over command of the army left the door open, for Muslim reinforcements to access the city.
In an attempt to hold off Muslim forces gaining access, Guillaume led the Templar army into battle, to save Christian forces. On the 26th August, Guillaume de Chartres Grand Master of the Order of the Knights Templar, was struck down by Muslim forces at Damiette. His wounds didn’t kill him, but a plague that spread through the Frankish armies left him weak. In 1219, he died of pestilence, a consequence of being wound at Damiette.