What major event concluded over 1300 years of unified Islam?

The fall of the Ottoman Empire at the end of the First World War is seen as the major event that marked the conclusion of over 1300 years of unified Islam, primarily because the Ottoman Empire was considered the last significant caliphate that existed in a form unifying a large Islamic community under a single political entity. With its dissolution in 1922, not only did it lead to the loss of the political structure that held Islamic territories together, but it also resulted in the fragmentation of Muslim regions into various nation-states. This fundamentally shifted the political landscape of the Muslim world and ended a long era of centralized Islamic authority.

While other events such as the Crusades, the Mongol invasions, and the establishment of the Saudi state had significant impacts on Islamic regions, they did not lead to the same degree of fragmentation or the cessation of a unified Islamic political structure that the fall of the Ottoman Empire did. The legacy of the empire’s collapse continues to affect contemporary geopolitics and the identity of Muslim societies around the world.