KABUL, AFGHANISTAN - Canada formally ended its combat role in Afghanistan on Thursday, closing a mission that has cost 157 soldiers their lives since 2002 -- casualties that shocked Canadians unaccustomed to seeing their troops die in battle.

The move adds to the burden of U.S. and Afghan troops who are trying to prevent a Taliban rebound in the militants' southern stronghold where Canadian troops had been fighting in their bloodiest conflict since the Korean War.

Canada is withdrawing its combat units as the sixth-largest troop-contributing nation, behind the United States, Britain, Germany, France and Italy.

Like Americans and Europeans, Canadians have grown weary of the war as it nears the 10-year mark. While 2,850 Canadian soldiers are going home, 950 others have started streaming into Afghanistan to help train Afghan security forces to take the lead role in securing the country by 2014, when other Western forces are to leave.

Canada passed the responsibility for two districts of Kandahar Province to U.S. forces at Kandahar Air Field during a ceremony held in a hall decorated with Canadian maple leaf flags. After remarks, handshakes and the exchange of military paperwork, troops held a moment of silence for their fallen comrades. Since 2002, 157 Canadian troops, one diplomat, one journalist and two aid workers have been killed in Afghanistan.

Military officials said the troop deaths and physical and psychological wounds suffered by soldiers must be seen in the context of the progress they helped make in Afghanistan. "We've seen a complete change," Canadian Brig. Gen. Dean Milner said in a video teleconference from Kandahar. "I think the Canadians have held the fort here for five or six years. With the surge of American forces and Afghan forces over the last year, we were able to accomplish a great deal."