FORT MEADE, Md. -- Lawyers for Army Pfc. Bradley Manning opened their case Monday in the sentencing phase of his trial by attacking commanders' decisions to send the young intelligence analyst to Iraq and let him keep his top-secret security clearance despite emotional outbursts and concerns about his mental health.

Manning faces up to 90 years in prison for disclosing reams of classified information through the anti-secrecy website WikiLeaks. His lawyers are presenting evidence in hopes of a lighter sentence.

Manning had a history of violent outbursts and psychological evaluations during his military training before and after he deployed in 2009. During his stateside training as an intelligence analyst, he had to give a classroom presentation about the dangers of disclosing classified information after he provided secret details about his schooling in online communications with relatives.

His brigade commander, Col. David Miller, testified the 2nd Brigade of the 10th Mountain Division deployed in the fall of 2009 with 10 to 15 per cent fewer intelligence analysts than the number authorized by the military. But Miller denied feeling any pressure to take soldiers who should not have deployed.

"In a counterinsurgency fight, you can always use more," he said.

Maj. Clifford Clausen, who headed the brigade's intelligence branch, said there was pressure to take every soldier.

"We were having a problem meeting strength. There was a pressure on the whole unit to deploy," he said.

Miller's executive officer Lt. Col. Brian Kerns said he had concerns before deployment about Clausen's leadership abilities.

"I think it was the right decision at the time to move forward with the individuals that we had because we didn't have anything better at the time that we could turn to," he said.

Clausen was removed from the position in early 2010 because of his failure to effectively communicate intelligence findings to commanders, Kerns and Miller testified.

Kerns and Clausen both said they received letters of reprimand as a result of an Army investigation into Manning's actions. They are among 15 people disciplined in the case.

In Iraq, Manning had several more emotional outbursts. One episode prompted commanders to remove the bolt from his rifle, rendering it unusable.

In December 2009, while being scolded for tardiness, Manning overturned a table, spilling a radio and computer onto the floor and had to be restrained, the supervisor, Sgt. Daniel Padgett, testified during a pretrial proceeding.

And in early May 2010, a few weeks before his arrest, Manning punched another supervisor in the face, prompting a commander to move him from the secure workplace to a supply room, but his security clearance wasn't immediately revoked.

Manning, a 25-year-old native of Crescent, Oklahoma, gave more than 700,000 documents and some battlefield video to WikiLeaks while working as an intelligence analyst in Iraq. He was convicted July 30 of 20 counts, including six federal Espionage Act violations, five theft counts, and a federal Computer Fraud and Abuse Act charge.

Manning says he leaked the material to expose wrongdoing and provoke discussion about U.S. military and diplomatic affairs.

The sentencing hearing is in its third week.