Identify two groups that brought about an end to the Byzantine Empire; describe what they each did.

The Byzantine Empire faced a number of threats from different fronts. The Byzantine Empire was engaged in long-running conflicts with both the Bulgarian and Serbian Empires. However, the two groups that played a major role in its decline were the crusaders or the Catholics of the Western Roman Empire and the Turks who later formed the Ottoman Empire.

The conflict between the Byzantine Empire and the Western Roman Empire revolved around religious differences. The Byzantine Empire identified with Orthodox Christianity while the Western Empire identified with Catholicism. These differences led to the sacking of Constantinople by the crusaders of the Western Empire resulting in the growing enmity between the two groups. These conflicts drained resources that would have otherwise been used in the growth and development of the Byzantine Empire.

Losses suffered by the Byzantine Empire made the region vulnerable to attacks by the Turks. The Turks took the opportunity to annex Byzantine lands. The Empire was forced to seek help from the Western Empire. However, the condition to renounce Orthodoxy for Catholicism was unpopular among the Byzantine people, who rejected the condition. This delayed the help from the Western Empire, and by the time compromises were made, it was too late, and the Empire fell to the Turks who later united to form the Ottoman Empire.