In 1104 Baldwin II of Edessa had attacked and besieged the city of Harran. For his further support Baldwin sought help from Bohemond I of Antioch and Tancred, Prince of Galilee. Bohemond and Tancred marched north from Antioch to Edessa to join with Baldwin and Joscelin of Courtenay, accompanied by Bernard of Valence the Patriarch of Antioch, Daimbert of Pisa the Patriarch of Jerusalem, and Benedict, the Archbishop of Edessa.

The Seljuks, under Jikirmish, governor of Mosul, and Sokman, the Artuqid lord of Mardin, gathered in the area of the Khabur, perhaps at Ras al-Ayn (Hellenistic Rhesaina). In May 1104 they attacked Edessa, perhaps to distract the crusaders from Harran, perhaps to take the city while the crusaders were elsewhere engaged.

According to Ibn al-Qalanisi, Tancred and Bohemund arrived at Edessa during the siege, but according to Chronicle of 1234 they arrived first at the gates of Harran. In any case, the Seljuks rode away from the crusaders, feigning a retreat and the crusaders followed.

The Seljuks feigned retreat in the preliminary skirmishes while the Crusaders continued their pursuit south. The contemporary chronicler Matthew of Edessa reports a pursuit of two days while Ralph of Caen reports three days.^[5] According to Ibn al-Athir, the main battle was fought twelve kilometres from Harran.

Most historians accept the accounts of Albert of Aachen and Fulcher of Chartres, who located the battle on the plain (planitie) opposite the city of Raqqa, Raqqa being about two days away from Harran.

Baldwin and Joscelin commanded the Edessan left wing while Bohemond and Tancred commanded the Antiochene right.^[6] Ralph of Caen says that the crusaders were caught unawares when the Seljuks turned to fight, so much so that Baldwin and Bohemond fought without armor.

During the battle itself, Baldwin's troops were completely routed, with Baldwin and Joscelin captured by the Turks.^[7] The Antiochene troops along with Bohemond were able to escape to Edessa. However, Jikirmish had only taken a small amount of booty, so he purloined Baldwin from Sokman's camp. Although a ransom was paid, Joscelin and Baldwin were not released until sometime before 1108, and 1109 respectively.

The battle was one of the first decisive Crusader defeats with severe consequences to the Principality of Antioch.^[8] The Byzantine Empire took advantage of the defeat to impose their claims on Antioch, and recaptured Latakia and parts of Cilicia. Many of the towns ruled by Antioch revolted and were re-occupied by Muslim forces from Aleppo. Armenian territories also revolted in favour of the Byzantines or Armenia. Furthermore, these events caused Bohemund to return to Italy to recruit more troops, leaving Tancred as regent of Antioch.

William of Tyre wrote that there was no battle more disastrous than this. Although Antioch recovered by the next year, the Byzantine emperor Alexius I Comnenus imposed the Treaty of Devol on Bohemond, which would have made Antioch a vassal of the empire had Tancred agreed to it. Antioch was again crushed at the Battle of Ager Sanguinis in 1119. Edessa never really recovered and survived until 1144 but only because of divisions among the Muslims.

• Bernard S. Bachrach and David S. Bachrach, 2005. The Gesta Tancredi of Ralph of Caen: A History of the Normans on the First Crusade. The first English translation. ISBN 0-7546-3710-7
• Beaumont, André Alden. "Albert von Aachen and the County of Edessa", in Louis J. Paetow, ed. The Crusades and Other Historical Essays. Presented to Dana C. Munro by His Former Students. New York, 1928, pp. 101–138, esp. 124-127.
• Fulcher of Chartres, A History of the Expedition to Jerusalem, 1095-1127, trans. Frances Rita Ryan. University of Tennessee Press, 1969.
• Heidemann, Stefan. Die Renaissance der Städte in Nordsyrien und Nordmesopotamien: Städtische Entwicklung und wirtschaftliche Bedingungen in ar-Raqqa und Harran von der beduinischen Vorherrschaft bis zu den Seldschuken. Islamic History and Civilization: Studies and Texts 40, Leiden, 2002, p. 192-197.
• Jörgensen, Christer (2007), "Harran, 1104." In Battles of the Crusades 1097-1444. Edited by Kelly Devries. London: Amber.
• Armenia and the Crusades, Tenth to Twelfth Centuries: The Chronicle of Matthew of Edessa. Trans. Ara Edmond Dostourian. National Association for Armenian Studies and Research, 1993.
• Nicholson, Robert Lawrence. Tancred: A Study of His Career and Work in Their Relation to the First Crusade and the Establishment of the Latin States in Syria and Palestine. Chicago, 1940, pp. 138–147.
• William of Tyre, A History of Deeds Done Beyond the Sea, trans. E.A. Babcock and A.C. Krey. Columbia University Press, 1943.