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Why did Emperor Alexius I Comnenus seek Western military help against the Seljuq Turks?

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Hagia Sophia: mosaic — Byzantine Empire The Virgin Mary holding the Christ Child (centre), Justinian (left) holding a model of the Hagia Sophia, and Constantine (right) holding a model of the city of Constantinople; mosaic from the Hagia Sophia, 9th century.

Emperor Alexius I Comnenus sought Western military assistance primarily because the Seljuq Turks posed an existential threat to the Byzantine Empire. Following the defeat of the Byzantine army at the Battle of Manzikert in 1071, the empire lost control over much of Anatolia, which had served as its primary source of military and economic strength.123

By the time Alexius ascended the throne in 1081, the Seljuq expansion had brought Islamic forces perilously close to Constantinople. The empire was further weakened by internal instability, civil wars, and external pressures from other fronts, including Norman invasions in the west and Pecheneg raids in the north.1243

Alexius’s appeal for aid, delivered to the Council of Piacenza in 1095, arrived at a moment when relations between the Eastern and Western branches of Christianity were beginning to improve following the schism of 1054. Pope Urban II responded to this request, viewing the provision of military support as a potential pathway toward restoring ecclesiastical unity between the East and the West.132