A population divided among nearly 600 ethnic groups and tribal units and a conspicuous split between a largely Arab population in the north and black, non-Muslim southerners meant that Sudan's government had a high potential for instability. Political movements based on these regional, tribal, religious, and socioeconomic divisions have been responsible for numerous breakdowns of authority. Nimeiri's autonomy solution for the south in 1972 ended the first civil war. His decision in 1981 to abolish the Southern Regional Assembly and the later redivision of the south into three regions, however, revived southern opposition and helped to reignite the southern insurgency. Dissatisfaction with Nimeiri's rule also grew in the north as economic distress became more acute. The 1985 military coup that ousted Nimeiri was preceded by massive demonstrations in Khartoum triggered by price increases of food staples. The traditional political parties that dominated civilian politics reemerged in 1986 after a year of transitional military rule. Most parties continued to reflect sectarian loyalties rather than to promote national interests. Unable to function effectively through shifting political coalitions and unable to end the war in the south, civilian authority was again overturned, to be replaced by the authoritarian rule of Bashir on June 30, 1989.

The new military government immediately invoked emergency legislation banning strikes and other work stoppages as well as unauthorized political meetings. Political parties and trade unions were dissolved and their property frozen or seized. Leading members of the main political parties were arrested, as were senior members of the Sudan Bar Association and other prominent figures thought to be unfriendly to the new regime. More than 100 trade unionists were detained, while others were dismissed from the civil service, the army, and the police.

Although some political prisoners had been released by early 1990, evidence of continued opposition to the military government brought harsh repressive measures. In December 1989, a prominent physician was sentenced to death (later commuted to imprisonment) for organizing a doctors' strike. Another doctor was sentenced to fifteen years' imprisonment. In March 1990, the government announced that it had crushed a coup conspiracy, arresting prominent members of the Umma Party and military officers. Less than a month later, the regime alleged that it had discovered another coup plot among the military and executed twenty-eight high-ranking officers whom it claimed were implicated.

Although the military government was widely unpopular, its ruthless suppression of any manifestation of discontent appeared to have frightened the internal opposition into silence. A number of exiled politicians active in the previous Sadiq al Mahdi government announced the formation of an opposition organization, the National Democratic Alliance, in early 1990. The SPLA radio station in Ethiopia allotted broadcasting time to the alliance, but the group, brought together by political expediency, had difficulty organic6f nizing effective opposition to the Bashir regime. Former armed forces chief of staff, Lieutenant General Fathi Ahmad Ali, was among the exiled dissidents and became head of the National Democratic Alliance. Military purges, however, had left the majority of active officers silent for fear of dismissal and loss of their commands. Infiltration of informers into the SPAF made any form of dissident activity risky. Curfews were imposed, and detachments of troops guarding bridges and other key points minimized the possibility of military action to topple the regime. At the Khartoum International Airport, the Airborne Division, which was considered loyal to the government was available at short notice to help repel a coup attempt.

The presence of as many as 1 million refugees from southern Sudan in the vicinity of Khartoum was potentially destabilizing, but the refugees were weak and too divided into ethnic and regional groups to be a political threat. Student groups had in the past been involved in demonstrations that contributed to the downfall of unpopular governments, but the loyalty of the majority of students was uncertain.

The small communist movement, with considerable support among educated Sudanese and involvement in student and union organizations, was among the opposition elements to the Bashir government. The Sudanese Communist Party (SCP) played an important role in the first years of Nimeiri's rule but was harshly suppressed and forced underground after participation in the unsuccessful coup against Nimeiri in 1971. Although Nimeiri's campaign of reconciliation with his political opponents in 1977 enabled some prominent SCP members to resurface, communists arrested for organizing strikes and demonstrations comprised the largest single group of political prisoners. The SCP's role in the urban demonstrations of 1985 contributed to Nimeiri's overthrow. The SCP became active in parliamentary politics in 1986 but was among the political groups banned by the Bashir regime. It joined with other parties in underground opposition to the military government. Several communists were rounded up and detained without charge after the 1989 coup, allegedly for instigating a protest against the government among students at the University of Khartoum.

Data as of June 1991