Awadallah retained his position as RCC deputy chairman and remained in the government as foreign minister and as an important link with leftist elements. Conservative forces, led by the Ansar, posed the greatest threat to the RCC. Imam al-Hadi al-Mahdi had withdrawn to his Aba Island stronghold in the Nile, near Khartoum, in the belief that the government had decided to strike at the Ansar movement. The Imam had demanded a return to democratic government, the exclusion of communists from power, and an end to RCC rule. In March 1970, hostile Ansar crowds prevented Nimeiri from visiting the island for talks with the imam. Fighting subsequently erupted between government forces and as many as 30,000 Ansar. When the Ansar ignored an ultimatum to surrender, army units with air support assaulted Aba Island. About 3,000 people died during the battle. The Imam escaped only to be killed while attempting to cross the border into Ethiopia. The government exiled Sadiq al Mahdi to Egypt, where Nasser promised to keep him under guard to prevent him from succeeding his uncle as head of the Ansar movement. After neutralizing this conservative opposition, the RCC concentrated on consolidating its political organization to phase out communist participation in the government. This strategy prompted an internal debate within the SCP. The orthodox wing, led by party secretary general Abd al Khaliq Mahjub, demanded a popular front government with communists participating as equal partners. The National Communist wing, on the other hand, supported cooperation with the government. Soon after the army had crushed the Ansar at Aba Island, Nimeiri moved against the SCP. He ordered the deportation of Abd al Khaliq Mahjub. Then, when the SCP secretary general returned to Sudan illegally after several months abroad, Nimeiri placed him under house arrest. In March 1971, Nimeiri indicated that trade unions, a traditional communist stronghold, would be placed under government control. The RCC also banned communist affiliated student, women's, and professional organizations. Additionally, Nimeiri announced the planned formation of a national political movement called the Sudan Socialist Union (SSU), which would assume control of all political parties, including the SCP. After this speech, the government arrested the SCP's central committee and other leading communists. The SCP, however, retained a covert organization that was not damaged in the sweep. Before further action could be taken against the party, the SCP launched a coup against Nimeiri. The coup occurred on July