Russia had conquered Central Asia in the 19th century by annexing the formerly independent khanates of Kokand and Khiva and the Emirate of Bukhara. After the Communists took power in 1917 and created the Soviet Union it was decided to divide Central Asia into ethnically-based republics in a process known as National Territorial Delimitation (or NTD). This was in line with Communist theory that nationalism was a necessary step on the path towards an eventually communist society, and Joseph Stalin's definition of a nation as being "“a historically constituted, stable community of people, formed on the basis of a common language, territory, economic life, and psychological make-up manifested in a common culture”".