The WikiLeaks case is by far the most voluminous release of classified material in U.S. history. Manning's supporters included Pentagon Papers leaker Daniel Ellsberg, who in the early 1970s spilled a secret Defense Department history of U.S. involvement in Vietnam.
The 7,000 pages of the Pentagon Papers showed that the U.S. government repeatedly misled the public about the Vietnam War.
The material WikiLeaks began publishing in 2010 documented complaints of abuses against Iraqi detainees, a U.S. tally of civilian deaths in Iraq, and America's weak support for the government of Tunisia — a disclosure that Manning supporters said helped trigger the Middle Eastern pro-democracy uprisings known as the Arab Spring.
The Obama administration said the release threatened to expose valuable military and diplomatic sources and strained America's relations with other governments.
Prosecutors said during the trial Manning relied on WikiLeaks and its founder Julian Assange for guidance on what secrets to "harvest" for the organization, starting within weeks of his arrival in Iraq in late 2009.
Federal authorities are looking into whether Assange can be prosecuted. He has been holed up in the Ecuadorean Embassy in London to avoid extradition to Sweden on sex-crimes allegations.