Growing war weariness and the reduction of tensions between the superpowers compelled South Africa, Angola, and Cuba to accede to the Tripartite Accord, under pressure from both the Soviet Union and the United States. South Africa accepted Namibian independence in exchange for Cuban military withdrawal from the region and an Angolan commitment to cease all aid to PLAN. PLAN and South Africa adopted an informal ceasefire in August 1988, and a United Nations Transition Assistance Group (UNTAG) was formed to monitor the Namibian peace process and supervise the return of refugees. The ceasefire was broken after PLAN made a final incursion into the territory, possibly as a result of misunderstanding UNTAG's directives, in March 1989. A new ceasefire was later imposed with the condition that the insurgents were to be confined to their external bases in Angola until they could be disarmed and demobilised by UNTAG.