A supporter of US Army Private First Class Bradley Manning protests outside the main gate before the reading of the verdict in Manning's military trial at Fort Meade, Maryland July 30, 2013.[Photo/Agencies]

"I think certainly that a conviction on that charge would have had a ripple effect," said Lisa Windsor, a retired Army colonel and former judge advocate. "I think it would have had certainly a chilling effect on anyone in the military who might decide that this is some sort of freedom of speech or whistleblower thing that they needed to engage in."

The judge did not give any reasons for her verdict from the bench, but said she would release detailed written findings. She did not say when.

Manning acknowledged giving WikiLeaks more than 700,000 battlefield reports and diplomatic cables, and video of a 2007 US helicopter attack that killed civilians in Iraq, including a Reuters news photographer and his driver. Prosecutors branded him an anarchist and traitor.

The defense portrayed the Crescent, Okla., native as a "young, naive but good-intentioned" figure. Manning said during a pretrial hearing he leaked the material to expose US military "bloodlust" and diplomatic deceitfulness but did not believe his actions would harm the country.

Besides the aiding the enemy acquittal, Manning was found not guilty of one espionage count involving his acknowledged leak of a video from a 2009 airstrike in Afghanistan. The judge found that prosecutors had not proved Manning leaked the video in late 2009. Manning said he started the leaks in February the following year.

Manning pleaded guilty earlier this year to lesser offenses that could have brought him 20 years behind bars, yet the government continued to pursue all but one of the original, more serious charges.

Rep. Howard "Buck" McKeon, R-Calif., chairman of the House Armed Services Committee, welcomed Tuesday's verdict.

"Bradley Manning endangered the security of the United States and the lives of his own comrades in uniform when he intentionally disclosed vast amounts of classified data," he said. "His conviction should stand as an example to those who are tempted to violate a sacred public trust in pursuit of notoriety, fame, or their own political agenda."

Some of Manning's supporters attended nearly every day of the two-month trial, protesting outside the Fort Meade gates wearing T-shirts with the word "truth" on them.

"I never in my heart ever thought that he was a traitor and I never thought he was trying to aid the enemy," Joe Brown of Silver Spring, Md., said outside the courtroom. "He's an American hero who saw things we did that he didn't think were right ... The killing of people unnecessarily."

The WikiLeaks case is by far the most voluminous release of classified material in US history. Manning's supporters included Pentagon Papers leaker Daniel Ellsberg, whose sensational leak of 7,000 pages of documents in the early 1970s exposed US government lies about the Vietnam War.

Reacting to Tuesday's verdict, Ellsberg said Manning's acquittal on aiding the enemy limits the chilling consequences of the WikiLeaks case on press freedoms.

"American democracy just dodged a bullet, a possibly fatal bullet," Ellsberg said. "I'm talking about the free press that I think is the life's blood of the democracy."

The material WikiLeaks began publishing in 2010 documented complaints of abuses against Iraqi detainees, a US 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.