South Sudan's independence was preceded by two civil wars, from 1955 to 1972 and from 1983 to 2005, in which 2.5 million people were killed and more than 5 million externally displaced. Relations between the two states have been marked by conflict over the Greater Nile Oil Pipeline and the disputed region of Abyei, even though Sudan was the first state to recognise South Sudan. In January 2012, South Sudan shut down all of its oil fields in a row over the fees Sudan demanded to transit the oil.