WASHINGTON -- Marine commandant Gen. James Amos has been cleared of allegations that he displayed favoritism toward a Marine during an investigation of an infamous video showing snipers urinating on the corpses of Taliban fighters in Afghanistan.

Amos was cleared by the Defense Department's inspector general's office, which said his conduct "was reasonable under the circumstances," according to a document reviewed by The Wall Street Journal.

Amos was accused by a Marine lawyer of giving preferential treatment to then-Maj. James B. Conway, an officer in the unit under investigation, by approving a promotion during the probe. The officer is the son of a former Marine commandant, Gen. James T. Conway.

Now-Lt. Col. Conway wasn't accused of wrongdoing and didn't appear in the video.

Made public in January 2012, the video came on heels of other U.S. missteps, including the burning of Qurans at Bagram Airbase, which triggered violent protests. The video was condemned by top U.S. officials, who feared it could set back the war effort in Afghanistan and bring more attacks on U.S. troops.

The four Marines videotaped urinating on the Taliban corpses were forced out of the Corps, and a Marine officer is facing disciplinary action.

Amos also has been accused of taking other steps to improperly intervene in the case. According to the report, Defense lawyers for Marines involved complain that he pressured other top officers to pursue harsh charges against the snipers in the video as well as officers who were accused of failing to stop them.

"It is the most aberrant behavior I have ever seen; it is improper," John Dowd, a lawyer for the Marine officer punished as part of the investigation, told the paper.

Maj. James Weirick, a Marine lawyer who has harshly criticized the way the service has handled the case, filed a complaint with the inspector general that then-Maj. Conway had received preferential treatment because he is the son of Amos' predecessor.

Dowd represents Capt. James Clement, who is facing expulsion from the Marine Corps for allegedly failing to take action against the four Marines involved in the urination video.

The Wall Street Journal reported that Dowd filed a letter with the Navy secretary this week asking that Clement be allowed to remain in the military. A board of inquiry didn't find he had been derelict in his duty, but ruled he failed to demonstrate leadership and recommended an honorable discharge.

In the letter, Dowd argued that Clement was only being pushed out because of the unlawful actions of Amos.

Clement's lawyers have pointed to a conversation between Amos and Lt. Gen. Thomas Waldhauser, who originally oversaw the investigation. The Journal reported that according to a statement by Waldhauser, Amos said in the Jan. 15, 2012, conversation that he wanted to "crush" the Marines involved, sending them to court-martial and removing them from the Corps, according to a legal affidavit filed by Dowd in the Clement case.

Defense officials familiar with Amos' account of the meeting dispute that description of the conversation.