Quantico, Virginia (CNN) -- Activists rallied outside the Marine Corps base at Quantico, Virginia, Sunday to applaud the man military officials suspect leaked scores of military documents to the WikiLeaks website -- a 22-year-old Army private named Bradley Manning.

"We are here to say that if he, indeed, was the whistle-blower, then we are proud of him," said Medea Benjamin, founder of anti-war group Code Pink. "In the United States that I know and love, transparency is a positive thing."

Manning, who served as an intelligence analyst in Iraq, is the military's focus in the investigation into the largest-ever intelligence leak in American history, to WikiLeaks.org.

He is being detained at Quantico pending a military investigation in a separate case, in which he's charged with eight violations of the U.S. Criminal Code, including for allegedly leaking a secret military video from the Iraq war to WikiLeaks.

Outside the Quantico gates, about 80 protesters chanted "Bradley Manning told their tale, war criminals off to jail" and held signs calling on the military to "Free Bradley Manning."

Many wore pink and seemed out-of-place in a small community where people sported military haircuts and displayed Marine bumper stickers on their cars.

Ray McGovern, who said he was formerly a CIA analyst, lauded Manning for allegedly releasing information about America's "war of aggression".

"What Bradley Manning has done is to give us as Americans the opportunity to realize what's really going on there," McGovern said.

"If Americans can't realize now that they have the ground truth, literally the ground truth from these Army reports, if they can't realize and move to end these kinds of wars, then there's very little hope for our children or our grandchildren."

About 300 yards away, a handful of counter-protesters wearing the military's trademark olive green held a poster that showed Manning with bloody hands. They called the leak treasonous.

"If Bradley Manning is the one that leaked these documents, he has already put his fellow soldiers at risk," said Jim Hanson, who writes for the pro-military website BlackFive.

"I think the military and the government have some things that should be kept secret. The public knows that ... There is no 'right to know' secret information."