Nato's mission over Libya is due to formally come to an end at one minute to midnight Libyan time on Monday.It follows the unanimous vote last week at the UN Security Council to end internationally military operations after seven months.In March, the council had authorised "all necessary measures" to protect civilians.The UN mandate came after then leader Colonel Muammar Gaddafi launched a deadly assault on protesters.Nato Secretary General Anders Fogh Rasmussen said that Operation Unified Protector was "one of the most successful in Nato history''.The first missions were flown on the evening of 19 March, as Colonel Gaddafi's forces approached the rebel-held city of Benghazi.With the help of America's massive military machine, Nato managed to sustain the Libya operation.Overall, its warplanes flew more than 26,000 sorties, including nearly 10,000 strike missions. More than 1000 tanks, vehicles and guns were destroyed, along with Colonel Gaddafi's command and control network.Mr Rasmussen said Nato's military forces had prevented a massacre and saved countless lives."We created the conditions for the people of Libya to determine their own future," he said.Despite the expected formal announcement that Nato's mission is over, Western powers were likely to be involved in Libya for some considerable time, says the BBC's Jonathan Beale.The Security Council decided to end its role, despite a call by Libya's National Transitional Council (NTC) for Nato to continue its military action.The Libyan envoy to the UN had said the NTC needed more time to assess its security needs. But diplomats said that the mandate to protect civilians had been accomplished, and any further security assistance would have to be negotiated separately.A small team of military advisers remains on the ground to aid the National Transitional Council. US and British experts are also trying to ensure that the surfeit of weapons in the country do not end up in the wrong hands.