Context: As of 1878, there were only three free Slavic states in the world: the Russian Empire, Serbia and Montenegro. Bulgaria was also free but was de jure vassal to the Ottoman Empire until official independence was declared in 1908. In the entire Austro-Hungarian Empire of approximately 50 million people, about 23 million were Slavs. The Slavic peoples who were, for the most part, denied a voice in the affairs of the Austro-Hungarian Empire, were calling for national self-determination. During World War I, representatives of the Czechs, Slovaks, Poles, Serbs, Croats, and Slovenes set up organizations in the Allied countries to gain sympathy and recognition. In 1918, after World War I ended, the Slavs established such independent states as Czechoslovakia, the Second Polish Republic, and the State of Slovenes, Croats and Serbs.

Question: What three free Slavic states were in the world as of 1878?
Answer: the Russian Empire, Serbia and Montenegro

Question: When were the Russian Empire, Serbia, and Montenegro the only free Slavic states in the world?
Answer: 1878

Question: Whose official independence was declared in 1908?
Answer: Bulgaria

Question: When were independent states as Czechoslovakia, the Second Polish Republic, and the State of Slovenes, Croats and Serbs established?
Answer: In 1918

Question: What was Serbia de jure vassal to in 1878?
Answer: Unanswerable

Question: When was Montenegro's independence declared?
Answer: Unanswerable

Question: How many people were in the Ottoman Empire?
Answer: Unanswerable

Question: What ended in 1878?
Answer: Unanswerable

Question: How many Slavs lived in Czechoslovakia?
Answer: Unanswerable