Answer:
The end of World War I
Step-by-step explanation:
The Austro- Hungarian and Ottoman Empires ruled Eastern Europe until World War I.
The tensions arising in the Austro-Hungarian Empire as nationalist feeling set off in 1914. This sense of urgency led to an attack on Serbia after the assassination of Archduke Francis Ferdinand. After the war, the Austro-Hungarian Empire was rapidly disintegrating into separate states based on nationality. World War I led to the breakup of the Austro- Hungarian, and Ottoman Empires and the creation of several new countries, including Czechoslovakia, Yugoslavia, etc.