The UN spent $1.6 billion from 1994 to 1998 in maintaining a peacekeeping force. The Angolan military attacked UNITA forces in the Central Highlands on 4 December 1998, the day before the MPLA's fourth Congress. Dos Santos told the delegates the next day that he believed war to be the only way to ultimately achieve peace, rejected the Lusaka Protocol, and asked MONUA to leave. In February 1999, the Security Council withdrew the last MONUA personnel. In late 1998, several UNITA commanders, dissatisfied with Savimbi's leadership, formed UNITA Renovada, a breakaway militant group. Thousands more deserted UNITA in 1999 and 2000.