Final answer:
The Russian Empire withdrew from World War I early due to the Russian Revolution of 1917, which overthrew the imperial government and led to the creation of the USSR.
Step-by-step explanation:
The country that dropped out of World War I early due to civil revolution and social chaos was the Russian Empire. This happened as a result of the Russian Revolution of 1917, which led to the collapse of the imperial government and the rise of the first communist country, the Union of Soviet Socialist Republics (USSR).
The revolution was partly triggered by the immense strain World War I placed on Russian society and its economy, as well as the widespread disgruntlement among the diverse populations within the Russian Empire.