A military jury met for about 20 minutes before giving the maximum sentence to Staff Sgt. Camilo Mejia, an infantry squad leader with the Florida National Guard.
"I have no regrets. Not one," Mejia said before his sentencing.
In his comments to the jury of four officers and four enlisted soldiers, Mejia said he was not afraid of going to jail. "I will take it because I will go there with my honor, knowing I have done the right thing," he said.
Mejia, 28, says he refused to return to his unit after a two-week furlough in October because he believes the war in Iraq is unjust. He turned himself in to the Army in March and sought status as a conscientious objector.
Military prosecutors argued that Mejia abandoned his troops and didn't fulfill his duty.
"He enjoyed all the benefits of the military, just not the duty," Capt. A.J. Balbo, the lead prosecutor, said in his closing argument. "The defense says he accomplished all his missions. Except the most important one — showing up."
Mejia's commander in Iraq, Capt. Tad Warfel, said the verdict would send a message that "deserters are punished, regardless of what their arguments are or their excuses."
Mejia told jurors that one of the turning points for him was an ambush his unit faced in Ramadi, when he said four soldiers were wounded by shrapnel and he saw an Iraqi civilian decapitated by U.S. machine gun fire.
"So things change, perceptions change," Mejia said. "You lose perspective of the value of human life. It happens."
Mejia was led out of the courthouse by military police with his hands cuffed behind his back to a waiting patrol car. Some civilian supporters shouted words of encouragement, including "Bravo, Camilo!"
Defense lawyer Louis Font said in his closing argument that Mejia made "an honest mistake of fact."
"This case clearly is about what was in the accused's mind," Font said. "He had an honest and reasonable view that because he had become a conscientious objector, he would not be required to serve in Iraq anymore."
Mejia's application to be an objector is being considered separately.
In his objector application, he also claims he saw Iraqi prisoners treated cruelly when he was put in charge of processing detainees last May at al-Assad, an Iraqi air base occupied by U.S. forces.
He did not mention specific abuse claims during his comments to the jury Friday, but told them that their decision, and the actions of American troops in Iraq, would be noticed around the world.
"I say that we're all on trial because the world is watching. They're looking at the decisions we make (such as) war crimes, abuse of prisoners," he said.