what is now south sudan was once part of the anglo-egyptian sudan. this part of the british empire became the republic of sudan when independence was achieved in 1956. after the first sudanese civil war, the southern sudan autonomous region was formed in 1972 and lasted until 1983. a second sudanese civil war soon developed and ended with the comprehensive peace agreement of 2005. later that year, the autonomous government of southern sudan was formed. south sudan became an independent state on 9 july 2011 at midnight local time, after a referendum held in january 2011. in the referendum, nearly 99% of voters wanted to separate from the rest of sudan.