At its peak the Ottoman Empire extended to eastern Europe, northern Africa, the Arab lands and included many Jews and Christians. Jews fled Europe for greater safety in Ottoman areas with over a million Jews there in 1900. By the dawn of the twentieth century the Ottoman Empire was considered "sick" and ripe for picking off territory. They did control access to the Black Sea which was key for trade with Russia. Russia, an antagonist to Turkey over centuries saw an opening. Italy saw an opportunity in Libya. Fighting in the Balkans, including Serbia and Bulgaria against the Ottoman Empire preceded World War I.
Mustafa Kemal abolished the caliphate in 1924 and was denounced many years later by Osama bin Laden for doing so. He is noted for running roughshod to modernize Turkey.
What can history tell us about today's turmoils? While finishing this up I heard Fareed Zakaria's guest Robert A Worth and then checked a book review. There is a lot of anger in the Mid-East. They all want change, but are not tolerant of different views. One view is that modernization has progressed technically, but socially the pace has been very slow. Sean McMeekin proclaims that the hatred has existed for a very long time, but had been controlled under the Ottoman regimes. Although boundaries may have been redrawn imperfectly they only complicate a difficult situation.