Passage: The dominance of the nomads ended in the 16th century as firearms allowed settled people to gain control of the region. The Russian Empire, the Qing dynasty of China, and other powers expanded into the area and seized the bulk of Central Asia by the end of the 19th century. After the Russian Revolution of 1917, the Soviet Union incorporated most of Central Asia; only Mongolia and Afghanistan remained nominally independent, although Mongolia existed as a Soviet satellite state and Soviet troops invaded Afghanistan in the late 20th century. The Soviet areas of Central Asia saw much industrialisation and construction of infrastructure, but also the suppression of local cultures and a lasting legacy of ethnic tensions and environmental problems.

Question: In which century did Soviet Union invade Afghanistan?
20th century