The schism between the Eastern Orthodox Church and the Western (or Roman) Church, which became definitive in the year 1054. Tension between the two Churches dated back at least to the division of the Roman empire into an Eastern and a Western part, and the transferral of the capital city from Rome to Constantinople in the 4th century. An increasingly different mental outlook between the two Churches resulted from the occupation of the West by formerly barbarian invaders, while the East remained the heirs of the classical world. This was exacerbated when the popes turned for support to the Holy Roman Empire in the West rather than to the Byzantine empire in the East, especially from the time of Charlemagne onwards. There were also doctrinal disputes, and arguments over the nature of papal authority. Matters came to a head in 1054 when the two Churches, through their official representatives, excommunicated and anathematized (formally denounced) each other. The breach was deepened in 1204 when the Fourth Crusade was diverted to Constantinople and sacked the city and a Latin (Western) Empire was established there for some time. There were various attempts to heal the schism, notably at the ecclesiastical councils of Lyons II (1274) and Florence (1439), but the reunions proved fleeting. These attempts were effectively brought to an end when the Ottoman Turks captured Constantinople in 1453 and occupied almost all of the former Byzantine empire for many centuries. It is only in recent years that the dialogue between the two Churches to heal the schism has been effectively re-opened.