Also, government witnesses testified the leaks endangered U.S. intelligence sources, some of whom were moved to other countries for their safety. And several ambassadors were recalled, expelled or reassigned because of embarrassing disclosures.
Prosecutors called Manning an anarchist and an attention-seeking traitor, while supporters have hailed him as a whistleblower and likened him to Daniel Ellsberg, the defense analyst who in 1971 leaked the Pentagon Papers, a secret history of U.S. involvement in Vietnam, to The New York Times and other newspapers.
That case touched off an epic clash between the Nixon administration and the press and led to a landmark Supreme Court ruling on the First Amendment.
The Obama administration has charged seven people with leaking to the news media, while only three people were prosecuted in all previous administrations combined.
Among those seven is Snowden, whose leak has triggered a fierce debate over security vs. privacy and strained U.S. relations with Russia, which is harboring him despite demands he be returned to this country to face charges.
In addition, the Justice Department has obtained the records of phones used by Associated Press journalists and emails of a Fox News reporter.
Also, a federal appeals court ruled recently that New York Times reporter James Risen cannot shield his source when he testifies at the trial of a former CIA officer accused of leaking information about a secret operation.
A lawyer for WikiLeaks founder Julian Assange, Michael Ratner, has suggested Manning's conviction could make it easier for federal prosecutors to get an indictment against Assange as a co-conspirator.
But other legal experts said the Australian's status as a foreigner and a publisher make it unlikely he will be indicted.