Cornell, who had fled to Canada where he expressed his objection to the war in Iraq, also was given a bad conduct discharge during the military proceedings at Fort Stewart.
The War Resisters Support Campaign, a Canadian anti-war group, said prosecutors had argued Cornell's appearance on television in Canada had helped undermine troop morale in the Middle East.
"Cliff is being punished for what he believes, for his comments to the press," said James Branum, the lawyer who represented Cornell during the court-martial. "Because he spoke out against the Iraq war, Cliff's sentence is harsher than the punishment given to 94 percent of deserters who are not penalized but administratively discharged."
Cornell, a specialist in the 39th Artillery Regiment at Fort Stewart, deserted to Toronto in 2005. Canadian authorities ordered the Mountain Home, Ark., native out of the country in February after Immigration Minister Jason Kenney turned down his request to stay in Canada on humanitarian and compassionate grounds.