Complex sentence: The repression started in 1860 when the Russian Empire waged a colonial war in Central Asia, the empire did not only destroy and conqueror the cities, but also they killed huge number of people.
Split into simpler sentences: The repression started in 1860 when the Russian Empire waged a colonial war in Central Asia. The empire did not only destroy and conqueror the cities, but they also killed a huge number of people.