The court-martial of Army Private First Class Bradley Manning has started in Fort Meade, Maryland.
Manning was arrested in 2010, accused of leaking hundreds of thousands of classified US government documents.
The former Army intelligence analyst has admitted that he gave the documents to the anti-secrecy group WikiLeaks.
He faces 20 years in prison for that.
Prosecutors also want a conviction on the charge of "aiding the enemy," which carries a possible life sentence.