Conversation so far:
when did the countries in central asia and the caucasus become independent
With the collapse of the Soviet Union in 1991, five Central Asian countries gained independence.
which five countries in central asia became independent in 1991
Five Central Asian countries gained independence — Kazakhstan, Uzbekistan, Turkmenistan, Kyrgyzstan, and Tajikistan.
why did the soviet union originally control the central asia countries
After the Russian Revolution of 1917, the Soviet Union incorporated most of Central Asia; only Mongolia and Afghanistan remained nominally independent.

Question: what did the soviet do to the countries
Self-contained rewrite: what did the soviet union do the central asia countries