Jihad is a centuries-old Arabic word that literally means "striving" or "struggle." While the term has become synonomous with "holy war," particularly against enemies perceived to be a threat to Islam, the broader use denotes a spiritual or psychological struggle undertaken to please Allah. Such a struggle can mean the struggle to be a better Muslim or to resist immorality.

The official break, sometimes referred to as the Great Schism, came in 1054, when Pope Leo IX excommunicated Michael Cerularius, the patriarch of Constantinople, and Cerularius anathematized (condemned) the pope in response. The two denominations, which had long been at odds over such doctrinal matters as whether the priesthood should be celibate, the nature of the Holy Spirit and the use of icons, were also politically and culturally divided, with the seat of the Orthodox church's authority resting in Constantinople while the Catholic church was based in Rome. Tension persists between the two churches even today, though attempts at reconciliation have been made, most notably in December of 1965, when Pope Paul VI and Patriarch Athenagoras simultaneously repealed their churches' mutual excommunications.