Finally, Africans were disappointed that the dream of a united Africa was not realized. Most Africans felt a shared sense of continuing victimization at the hands of the West and were convinced that independence had not ended Western interference in and domination of African affairs. Many African leaders were angered when Western powers, led by the United States, conspired to overthrow the radical Congolese politician Patrice Lumumba in Zaire in the early 1960s. The episode reinforced their desire to form the Organization of African Unity as a means of reducing Western influence. But aside from agreeing to adopt a neutral stance during the Cold War, African states had difficulty achieving a united position on many issues, and their disagreements left the region vulnerable to external influence and even led to conflict. During the late 1980s and early 1990s, border disputes festered in many areas of the continent and in some cases—as with Morocco and a rebel movement in the Western Sahara and between Kenya and Uganda— flared into outright war. Even within many African nations, the concept of nationhood was undermined by the renascent force of regionalism or tribalism. Nigeria, with the largest population on the continent, was rent by civil strife during the late 1960s when dissident Ibo groups in the southeast attempted unsuccessfully to form the independent state of Biafra. Ethnic conflicts broke out among hostile territorial groups in Zimbabwe (the former Southern Rhodesia) and in several nations in Central Africa. In Kenya, Luo tribal leader Tom Mboya was assassinated, presumably because rival groups feared that he would be selected to succeed the charismatic Kikuyu president Jomo Kenyatta. Another force undermining nationalism in Africa was pan-Islamism. Its prime exponent in Africa was Egyptian president Gamal Abdel Nasser. After Nasser’s death in 1970, the torch of Islamic unity in Africa passed to Libyan president Muammar Qadhafi, whose ambitions to create a greater Muslim nation in the Sahara under his authority led to conflict with neighboring Chad. The Islamic resurgence also surfaced in Ethiopia, where Muslim tribesmen in Eritrea (the former Italian colony of Eritrea had been joined with Ethiopia in 1952) rebelled against the Marxist regime of Colonel Mengistu in Addis Ababa.