Captain Rogelio "Roger" Maynulet, 30, was convicted on Thursday of assault with intent to commit voluntary manslaughter, which carries a 10-year maximum sentence. He maintained the killing was "honorable" because he wanted to end the man's suffering.
Maynulet stood to attention as Lieutenant Colonel Laurence Mixon, the head of the six-member panel hearing his case, announced the sentence. He then embraced his two defence lawyers, and his wife, Brooke, who burst into tears.
Prosecutors had sought a three-year prison sentence for Maynulet in addition to dismissal from the armed forces.
They argued that he deserved a severe penalty to send a signal that such behavior would not be tolerated.
"You commit a serious crime, you are out of the army. This is not what we do here," prosecutor Major John Rothwell said before sentence was passed.
The soldiers may have been told
the car carried Muqtada al-Sadr
"What kind of institution does the US army become if assault with the intent to commit voluntary manslaughter is an honorable act?"
In an emotional plea to the court for leniency, Maynulet's mother, Carmen, said she was "very, very proud" of her son. The Cuban immigrant said she flies the American flag she received when she became a US citizen in her back yard, next to a tree tied with a yellow ribbon that she said would remain until the end of her son's court-martial.
"Please let my son come home," she said tearfully. Maynulet was convicted of a lesser charge than the one he originally faced, assault with the intent to commit murder.
"I'm happy to have my life back, but I'm being forced out of my family"
Roger Maynulet, former captain
He said he was sorry to be kicked out of the army, which he called his family.
"It's bittersweet," he said after being sentenced. "I'm happy to have my life back, but I'm being forced out of my family. Still, I'm definitely happy I'm not in confinement."
On 21 May 2004, Maynulet was leading his 1st Armoured Division company on a mission near Kufa, south of Baghdad, when it was told a car thought to be carrying what the US army called a "high-level" target was heading towards them.
No details of the mission have been released, but it has been widely reported the company was told cleric Muqtada al-Sadr, who led uprisings against US-led forces in Iraq last year, was thought to be in the car with the driver.
The company chased the vehicle and fired at it. A passenger who was slightly wounded fled and was later apprehended, while the driver was pulled from the car with serious head injuries and pronounced untreatable by a medic.
Maynulet, praised by his peers during the trial as a dedicated soldier and promising officer, then shot the driver twice. The killing was filmed by a US drone surveillance aircraft.
After sentencing, Maynulet said he hopes the court-martial would serve as an example for troops in Iraq.
Asked by reporters for a message to the troops, he said: "Do your best, treat every Iraqi as a human being, use your training to provide every opportunity for them to enjoy their life."
Maynulet's lawyer, Captain Will Helixon, called him an outstanding soldier who started many projects in Iraq and was responsible for the arrest of 1000 fighters. He said the conviction was penalty enough.
Colonel Michael Ryan, who commanded Maynulet in Bosnia and testified during the trial, took a similar view.
"I think the outcome was the proper outcome, and I was pleased with the sentence," he said.
"If you look at the total event, justice was served on both sides."