Q: In this task, you are given a question and a context passage. You have to answer the question based on the given passage.
The acronym for the soverign state that existed in the past from 1922-1991 was?, Context: The post-Imperial nature of Russian subdivision of government changed towards a generally autonomous model which began with the establishment of the USSR (of which Russia was governed as part). It was liberalized in the aftermath of the Soviet Union, with the reforms under Boris Yeltsin preserving much of the Soviet structure while applying increasingly liberal reforms to the governance of the constituent republics and subjects (while also coming into conflict with Chechen secessionist rebels during the Chechen War). Some of the reforms under Yeltsin were scaled back by Vladimir Putin.
A:
USSR