Beginning in the fifth Century C.E. the two parts of the Roman empire began to grow apart. In contrast to the security and stability of the east, the West experienced constant warfare with barbarian tribes.  In 410 AD,the city of Rome itself was overrun by the Vandals. Again in 45? the  city once again was sacked, this time by the Visgoths. The movement of Barbrian tribes throughout Europe isolated the western empire from the east.

As a result of this isolation from one another, each developed its unique culture and social structures. In addition, language became problem.  At the height of the Roman Empire, most people (or at least most rulers and educated individuals) spoke both Greek and Latin. As the west and east became more isolated from one another, there was little need for people to be bilingual.  Consequently, the east increasinlgy spoke only Greek while the West spoke only Latin or the languages of the "barbarians".

Set a climate where a division was almost inevitable.

Two events proved to be decisive.

1.Papal claims of supremacy.  Ran contrary to the east's understanding of the councilar nature of the Church.

2. A single Latin Word "filioque."  First inserted in the eighth century in Spain, then in the churches of France and Germany.