Prior to the First Crusade, Bohemond had participated in attacks on the Byzantine Empire commanding the Norman forces during hostilities from 1080-1085.He was the eldest son of the Norman adventurer Robert Guiscard and when his father died in 1085 the Norman attacks on Byzantine territory ended and the dispute was resolved by Pope Urban II. It was then that Bohemond became the prince of Otranto.
In 1096 Bohemond joined the French forces headed to the Holy Land in what would later become known as the First Crusade. In spite of his previous hostilities with Alexius I, Bohemond ultimately swore an oath to the Emperor while passing through Constantinople on his way to the Holy Land. In 1098 following the capture of Antioch, Bohemond made himself prince of the city. In doing so, he broke his oath to Alexius I to return such re-conquered lands, but he cited the lack of promised assistance from the emperor to argue that the oath was not valid in this case.
Bohemond's ascension to ruler of the city of Antioch became a source of controversy during and after the crusade and became the basis for some claims that the crusades were about the conquest and colonization of the Holy Land. Yet this perspective does not take into consideration the numerous cites and areas that were returned to the Byzantine Empire in the wake of military victory by the crusaders. For example, Alexius I's daughter, Anna Comnena, in her account of her father's reign notes for the shrewdness of her father's dealings with the crusaders whom returned many lands and cities to Byzantine control.
In the year 1100, Bohemond was caputured by Muslims and not released until 1103. Again in 1109 Bohemond was defeated by Muslims at Harran and never returned to Antioch. His relative Tancred ruled as his regent in his absence. The best account of Bohemond's exploits during the First Crusade comes from the anonymous author of the Gesta Francorum, who traveled with the prince and was an eyewitness to many events.