Ottoman entry into World War I.
The Ottoman Empire's entry into World War I began when two recently purchased ships of its navy, still crewed by German sailors and commanded by their German admiral, carried out the Black Sea Raid, a surprise attack against Russian ports, on 29 October 1914. Russia replied by declaring war on 1 November 1914 and Russia's allies, Britain and France, then declared war on the Ottoman Empire on 5 November 1914. The reasons for the Ottoman action were not immediately clear. The Ottoman government had declared neutrality in the recently started war, and negotiations with both sides were underway.
This decision would ultimately lead to the deaths of hundreds of thousands of Ottoman citizens, the Armenian genocide, the dissolution of the empire, and the abolition of the Islamic Caliphate.