Complex sentence: However in early 20th century, under Soviet rule, kazakhs saw their biggest depopulation due to major famines of 1920s and 1930s, which were caused by Collectivization in the Soviet Union.
Split into simpler sentences: However in early 20th century, under Soviet rule, kazakhs saw their biggest depopulation due to major famines of 1920s and 1930s. Which were caused by Collectivization in the Soviet Union.