South Korean troops are leaving Iraq, bringing to an end a mission that focused on rebuilding hospitals, roads and schools but which divided South Korea's people. Some South Koreans believed participating in the Iraq operation would strengthen ties to the United States. Critics argued the mission was part of an unjustified war. The departure of the "Zaytun" contingent - the Arabic word for olive and the troops' codename for their mission - is the latest exodus from dwindling US-led coalition. The South Koreans are among troops from 13 countries being sent home in advance of the Dec. 31 expiration of the UN mandate that authorized military operations in Iraq. A ceremony to mark the end of the mission was scheduled Monday in Irbil, the capital of the Kurdish self-ruled region 350 kilometers north of Baghdad. At its height, the coalition numbered about 300,000 soldiers from 38 countries - 250,000 from the United States, about 40,000 from Britain, and the rest ranging from 2,000 Australians to 70 Albanians.