(Reuters) - Smoke, the Iraqi donkey whose journey from a desert battleground to a peaceful retirement in the United States captured the attention of the world, has died in Nebraska.

Smoke became lethargic and died this week after frolicking with miniature horses at Miracle Hills Ranch and Stable north of Omaha. Smoke had served as an equine therapy animal to help veterans with post-traumatic stress disorder.

Smoke's Facebook page has friends from around the world.

Smoke was taken in by U.S. Marines after he showed up malnourished and wounded at Camp Taqaddum in Anbar province in 2008. Regulations prohibited keeping the donkey, but Marine Colonel John Folsom of Omaha, then commander at the camp, found a Navy psychologist to designate Smoke as a therapy animal because he reduced stress among Marines.

The donkey learned to walk into offices and open desk drawers to find apples, carrots and other treats planted there by Marines. Deployed dads sent their children pictures and stories of Smoke.

U.S. Army troops who relieved Marines at the camp turned the donkey over to a local sheikh. Folsom, now retired, tracked down the donkey and cut through layers of red tape to bring him to Nebraska last year. He said Smoke may have died of colic.

"He was a great little donkey," Folsom said.