In October 1999, the United Nations agreed to send peacekeepers to help restore order and disarm the rebels. The first of the 6,000-member force began arriving in December, and the UN Security Council voted in February 2000 to increase the force to 11,000, and later to 13,000. But in May, when nearly all Nigerian forces had left and UN forces were trying to disarm the RUF in eastern Sierra Leone, Sankoh's forces clashed with the UN troops, and some 500 peacekeepers were taken hostage as the peace accord effectively collapsed. The hostage crisis resulted in more fighting between the RUF and the government as UN troops launched Operation Khukri to end the siege. The Operation was successful with Indian and British Special Forces being the main contingents.