History of Sudan
The modern Republic of Sudan was formed in 1956 and inherited its boundaries from Anglo-Egyptian Sudan, established in 1899. For times predating 1899, usage of the term "Sudan" for the territory of the Republic of Sudan was somewhat anachronistic, and may have referred to the more diffuse concept of the Sudan.
Sudan
Under the Delimitation, Sudan's border with Abyssinia was contested by raiding tribesmen trading slaves, breaching boundaries of law. In 1905 Local chieftain Sultan Yambio reluctant to the end gave up the struggle with British forces that had occupied the Kordofan region, finally ending the lawlessness. The continued British administration of Sudan fuelled an increasingly strident nationalist backlash, with Egyptian nationalist leaders determined to force Britain to recognise a single independent union of Egypt and Sudan. With a formal end to Ottoman rule in 1914, Sir Reginald Wingate was sent that December to occupy Sudan as the new Military Governor. Hussein Kamel was declared Sultan of Egypt and Sudan, as was his brother and successor, Fuad I. They continued upon their insistence of a single Egyptian-Sudanese state even when the Sultanate of Egypt was retitled as the Kingdom of Egypt and Sudan, but it was Saad Zaghloul who continued to be frustrated in the ambitions until his death in 1927. 
From 1924 until independence in 1956, the British had a policy of running Sudan as two essentially separate territories, the north and south. The assassination of a Governor-General of Khartoum in Cairo was the causative factor; it brought demands of the newly elected Wafd government from colonial forces. A permanent establishment of two battalions in Khartoum was renamed the Sudan Defence Force acting as under the government, replacing the former garrison of Egyptian army soldiers, saw action afterwards during the Wal Wal Incident. The Wafdist parliamentary majority had rejected Sarwat Pasha's accommodation plan with Austen Chamberlain in London; yet Cairo still needed the money. The Sudan Government's revenue had reached a peak in 1928 at £6.6 million, thereafter the Wafdist disruptions, and Italian borders incursions from Somaliland, London decided to reduce expenditure during the Great Depression. Cotton and Gum exports were dwarfed by the necessity to import almost everything from Britain leading to a balance of payments deficit at Khartoum.