The court martial for a US soldier accused of leaking large numbers of classified documents to Wikileaks began in Fort Meade, Maryland, on Monday.
Private Bradley Manning sent 250,000 diplomatic cables and 500,000 battlefield reports from Afghanistan and Iraq to the web site in 2009 and 2010. He was arrested three years ago.
He has pleaded guilty to 10 of the 22 charges against him, but not to the most serious charge - aiding the enemy.
If found guilty, Private Manning, 25, faces a sentence of up to life in prison.
In opening statements on Monday, the prosecutor said the about a soldier who "harvested" hundreds of thousands of documents and dumped them onto the internet where they could be of use to the country's enemies.
Captain Joe Morrow said Private Manning used his military training to gain the notoriety he craved and attempted to hide what he had done at every step of the process.
He added that Osama bin Laden had gained access to some of the Wikileaks information - and had used it.
The BBC reports the prosecution intends to introduce blog entries, a computer, a hard drive and an SD card as evidence against Private Manning.
Defense lawyer David Coombs said the accused was was "young, naive and good-intentioned" when he arrived in Iraq.
But in late 2009, he saw his comrades celebrating because no US soldiers had been hurt, after an Iraqi died in an attack.
After that incident, he said Private Manning began collecting information he thought would "make the world a better place" if public.
The BBC reports the court martial is expected to take all summer.