Why are North Sudan and South Sudan fighting?

The Second Sudanese Civil War (the one Salva lives through) begins in 1983 when the Sudanese People’s Liberation Movement (SPLM), led by John Garang, attacks the north for abolishing south Sudan’s autonomy. Numeiri had begun to abrogate parts of the agreement, imposing Shari’a law across the country. The Democratic Unionist Party, a part of Sudan’s ruling coalition government, drafts a cease-fire, but it is not implemented. Over the course of this conflict, between 1-2 million civilians are killed. The United Nations sends in thousands of peacekeepers and tries to assist with the widespread famine.