In 1773, a Don Kozak, Yemelyan Pugachev (Russian: Емельян Пугачёв), led a rebellion against the Russian Empire. This peasant/kozak/tartar revolt, brought on by the social injustices of the Russian social system, spread quickly throughout the territory of Eastern European Russia, even posing a threat to Moscow itself. Russia was vulnerable due to the ongoing war with Turkey that took away from the troop garrisons in the east. Pugachev eventually claimed to be Empress Catherine the Great's deceased huband, Peter III, and proclaimed himself emperor. He instantly announced the end of serfdom, taxation, and military service. Pugachev was later defeated and turned over to Catherine who had him executed in 1774. This rebellion caused Catherine to introduce a new system of government in 1775.