Sierra Leone has played a significant part in modern African political liberty and nationalism. In the 1950s, a new constitution united the Crown Colony and Protectorate, which had previously been governed separately. Sierra Leone gained independence from the United Kingdom on 27 April 1961 and became a member of the Commonwealth of Nations. Ethnic and linguistic divisions remain an obstacle to national unity, with the Mende, Temne and Creoles as rival power blocs. Roughly half of the years since independence have been marked by autocratic governments or civil war.