Opening the court-martial of U.S. Army Pfc. Bradley Manning, a military prosecutor charged Monday that he “harvested” a massive trove of classified information from secure networks and made it available to America’s enemies by dumping it onto the Internet.

In a nearly hourlong statement to a packed courtroom, Capt. Joe Morrow described ways in which he said the disclosure of this information put the lives of Manning’s fellow soldiers “at risk.” The trial opened at this army installation 40 km northeast of Washington more than three years after Manning was arrested in Iraq in connection with the largest leak of classified documents in U.S. history.

“This is a case about a soldier who harvested hundreds of thousands of documents and dumped them on the Internet where they would be available to the enemy,” Morrow said. A slide show outlining “key evidence” that the prosecution intends to present included information from an external hard drive of Manning’s personal computer and chat logs.

The prosecutor said the judge would gain a sense of an intelligence analyst who was leaking documents to whistle-blower website WikiLeaks almost from the moment of his November 2009 arrival at Forward Operating Base Hammer in Iraq. Morrow said Manning would “package” information and transmit it within a “couple of hours.”

The prosecution will seek to prove its case through presenting extensive forensic evidence from Manning’s work and personal computers, various pieces of digital media and logs of conversations Manning had with both Julian Assange of WikiLeaks and hacker Adrian Lamo.

Morrow concluded his opening remarks by saying that Osama bin Laden requested and received a copy of internal U.S. military logs of the war in Afghanistan from another member of al-Qaida. Manning has admitted to providing these war logs, consisting of more than 91,000 documents, to WikiLeaks, which subsequently released about 75,000 of them.

Defense attorney David Coombs, in an opening statement that followed Morrow’s, addressed Manning’s motive for leaking the information to WikiLeaks, portraying the defendant as an idealistic and naive young soldier.

Coombs described an incident that he said Manning observed when he first arrived in Iraq. A convoy had been hit by an improvised explosive device, but once Manning’s fellow soldiers knew no U.S. troops were killed, they were relieved and happy, Coombs said. When the news came that an Iraqi involved in the incident had died, the mood did not change. Manning was disturbed by this and started to reassess the reasons he was in Iraq, Coombs said. It was then that Manning “started to struggle,” the defense attorney said.

Coombs argued that Manning believed the information he was releasing was already basically in the public domain. For example, he said Manning knew that much of the information he leaked about assessments of detainees at Guantanamo Bay had already been released by the Pentagon.

“He knew a lot of people didn’t need to be there, held there year after year with no hope,” Coombs said. Manning also thought the information might be of value to the attorneys representing the detainees or ultimately of some historical importance, the attorney said.

Coombs portrayed Manning as a soldier who hoped to make a difference by releasing this information. He described Manning as “young, naive and good-intentioned.”Federal authorities are looking into whether WikiLeaks founder Julian Assange can also be prosecuted. He has been holed up in the Ecuadorean Embassy in London to avoid extradition to Sweden on sex-crimes allegations.

“This is not justice; never could this be justice,” Assange said Monday. “The verdict was ordained long ago. Its function is not to determine questions such as guilt or innocence, or truth or falsehood. It is a public relations exercise, designed to provide the government with an alibi for posterity. It is a show of wasteful vengeance; a theatrical warning to people of conscience.”

Testifying Monday afternoon were two members of the army’s Criminal Investigation Command — Special Agents Thomas Smith and Toni Graham — and Manning’s former roommate in Iraq, military police officer Eric Baker.

Smith, called as the first witness in the trial, testified that he helped secure the scene where Manning worked, as well as his personal living space in Iraq. Smith said he arrived at FOB Hammer on May 27, 2010, by helicopter and seized two secure computers on which Manning generally worked.

Smith said he found writable CDs in Manning’s housing unit. In one case marked as containing an Arabic language training CD, he found Apache helicopter video that showed the deaths of two Reuters news agency employees. The CD was marked “Reuters FOIA” in a black Sharpie.

He said he placed all the evidence in brown paper bags and eventually put them in an evidence footlocker. He said he ran out of paper bags while collecting evidence.

Detained by the military since his arrest in Iraq, Manning is the central figure in the latest and most prominent in a series of leak prosecutions under the administration of President Barack Obama. After months of pretrial hearings, motions and disputes over the use of classified information and public access to proceedings, the trial began in a spare courtroom behind Fort Meade’s guarded gates.

Manning, a boyish-looking 25, is accused of passing more than 700,000 government and military files to WikiLeaks. The material, which was widely disseminated, included videos of airstrikes that killed civilians, sensitive diplomatic cables and military reports from Iraq and Afghanistan.

He faces 20 charges, including a military charge of aiding the enemy, which could send him to prison for life without parole. He is also charged with violating the Espionage Act, a 1917 law created to try spies and traitors, which carries severe penalties.

In pretrial proceedings, Manning admitted leaking the material, saying he intended to “spark a domestic debate over the role of the military and our foreign policy in general.” He has offered to plead guilty to 10 lesser charges relating to the misuse of classified information, which could send him to prison for 20 years.

The prosecution’s insistence on proceeding with the two most serious charges, with their harsh penalties, has led even some critics of Manning’s actions to question whether the government is going too far.

Elizabeth Goitein, co-director of the Brennan Center for Justice’s Liberty and National Security Program, called Manning’s leaks “reckless” and “a data dump.” But she said that “he is not an enemy of the state” and that putting him behind bars for life “is overreaching.”

For its part, the prosecution said Manning must be held accountable. “Pfc. Manning was a U.S. analyst who we trained and trusted to use multiple intelligence systems . . . and he used that training to defy our trust,” army Maj. Ashden Fein, a prosecutor, said in one pretrial hearing.

Manning, he said, “knowingly engaged in a 6-month-long criminal enterprise of harvesting classified information” to send to WikiLeaks, “while knowing and understanding that enemies would have access to the information.” The enemies, Fein said, include al-Qaida.

The differences of opinion over Manning, a former army intelligence analyst, extend to the core of the case. Since his arrest in Iraq in May 2010, he has become a polarizing figure of international stature. Supporters see him as a heroic whistle-blower; critics view him as a traitor who harmed the nation and put lives at risk. He is even a figure in a new documentary film that focuses on WikiLeaks founder Assange, who is holed up in the Ecuadoran Embassy in London to avoid questioning in Sweden about sex crimes that two women have accused him of committing.

The treatment of Manning at times over the past three years — his clothes were taken away, and he was held in isolation — has led to international protests. And the military’s decision to withhold judicial rulings from the public has led to lawsuits.

Manning’s supporters held a protest march and rally outside Maryland’s Fort Meade on Saturday. One sign carried by protesters read, “Bradley Manning: Jailed for exposing war crimes.”

Barring a last-minute plea deal, the court-martial will be one of the biggest military trials since the cases stemming from the My Lai massacre in the Vietnam War. The process is expected to last at least 12 weeks, and the government plans to call 150 witnesses — 24 of them in partially closed sessions to prevent what the judge, army Col. Denise Lind, called “spillage of classified information.”

Manning opted to be tried by a judge rather than a jury of military members. Lind, who has presided over the pretrial hearings, has granted Manning 112 days’ credit toward his sentence if he is convicted, to compensate for his treatment.

Analysts are divided on how tough a challenge prosecutors face to win convictions on the most serious charges. The Brennan Center’s Goitein said that under a ruling by Lind, prosecutors will have to prove only that Manning had “reason to believe” that the documents disclosed could be used to harm the United States or to aid a foreign power. They need not prove that he intended to harm the U.S. “I suspect that the government can meet this burden on at least some of the counts,” Goitein said.

But some former prosecutors said it could be difficult to prove intent to harm the country.

Even some of Manning’s critics argue that his disclosures served the public interest in some instances. They cite his leak of a video showing an Apache helicopter assault in Baghdad that killed Iraqi civilians and two journalists, the disclosure of risk assessments for several dozen Guantanamo Bay detainees showing no record of why they were transferred to the military prison, and accounts of unreported civilian deaths in Afghanistan and Iraq.

On the other hand, they argue that some disclosures put foreign relations or even lives at risk with no obvious benefit to public debate. One example is the disclosure of the names of Afghan informants cooperating with allied forces, which put them in danger and forced steps to find and protect them.