An American lieutenant colonel pleaded guilty to beating an Iraqi detainee and threatening to kill him during an interrogation, but will be fined and allowed to retire rather than face a court-martial, the military said Saturday.

Lt. Col. Allen B. West (search) was found guilty of three counts of aggravated assault and one count of communicating a threat, according to a statement from the divisional press center.

West is the most senior officer of the 4th Infantry Division (search) to face disciplinary proceedings in Iraq. His punishment was reduced because of his good record and the difficult environment, the military said.

At a military pretrial hearing Friday, Gen. Raymond Odierno (search), who commands 4th Infantry Division based in Tikrit, fined West $5,000, relieved him from his post and forwarded his request for retirement next spring for approval.

"He will return to 4th Infantry Division's headquarters in Fort Hood, Texas, until his retirement," the division said in the statement.

West was not available to speak with reporters at the base in Tikrit (search), 100 miles north of Baghdad.

West pleaded guilty to punching and to firing a pistol near the prisoner, Yahya Jhodri Hamoodi, on Aug. 20, while interrogating him in al-Taji, just north of Baghdad. West also threatened to kill the detainee if he did not talk, according to the statement.

The division said West "disobeyed laws, ignored orders ... and mortgaged future discipline in his unit by compromising his credibility."

"While his crimes merit a court martial, mitigating factors ... were considered including the stressful environment ... and Lt. Col. West's record as an officer and commander," the military said.