If anyone knows what Edward Snowden — the IT contractor at the center of an ongoing uproar over the NSA's PRISM program — is going through, it's Daniel Ellsberg. "In my estimation, there has not been in American history a more important leak than Edward Snowden's release of NSA material — and that definitely includes the Pentagon Papers 40 years ago," Ellsberg wrote in The Guardian.

It was Ellsberg, of course, who released those papers to The New York Times in 1971, revealing how the U.S. government had misled the American public about the Vietnam War. As a result, Ellsberg was charged with six violations of the Espionage Act, and faced a maximum of 115 years in prison if found guilty.

The charges were dropped after it was discovered that the Nixon administration had sent two men to burglarize the office of Ellsberg's psychoanalyst, and tried to tempt the judge presiding over the case with an offer to become director of the F.B.I.

What kind of charges Snowden will face are unknown, although he told The Guardian that he expects to be charged under the Espionage Act, just like Ellsberg. Another whistleblower Ellsberg has publicly supported, Bradley Manning, is currently facing a life sentence for "aiding the enemy."

Both risked their freedom and public derision to release classified information, which is why Ellsberg said he feels connected to them:

I have been saying now for three years that I identify with Bradley Manning, though he got there first. He arrived at his decision at 22, while it took me until I was 40, or 39.

But I identify even more with Snowden, just from what I’ve seen in the last few hours [since the Guardian published his name and its interview with him earlier Sunday]. He’s older, he had higher access, he had a better salary than Manning. His life was like mine. It’s very easy for me to identify with his choice, his decision, his performance. [The Daily Beast]

However, some commentators were hesitant to put Snowden and Manning on equal footing with Ellsberg.

"Ellsberg was a veteran who had spent nearly a decade thinking about his war," Nicholas Thompson wrote in The New Yorker. "Manning and Snowden were more impulsive: They took files and dumped them."

Thompson's colleague, Jeffrey Toobin, went further, calling Snowden "a grandiose narcissist who deserves to be in prison."

Ellsberg would certainly object to the idea that Manning and Snowden simply dumped a bunch of documents. All three of them practiced restraint, Ellsberg argued in The Guardian:

There are legitimate reasons for secrecy, and specifically for secrecy about communications intelligence. That's why Bradley Mannning and I — both of whom had access to such intelligence with clearances higher than top-secret — chose not to disclose any information with that classification. And it is why Edward Snowden has committed himself to withhold publication of most of what he might have revealed.

But what is not legitimate is to use a secrecy system to hide programs that are blatantly unconstitutional in their breadth and potential abuse. Neither the president nor Congress as a whole may by themselves revoke the fourth amendment — and that's why what Snowden has revealed so far was secret from the American people. [The Guardian]

It's worth keeping in mind that Snowden's identity was revealed only a couple of days ago. Reporters are still confirming his story and investigating his past.

Ultimately, how Manning and Snowden are remembered depends on how the U.S. looks back on the war on terror, as well as the U.S.'s invasions of Iraq and Afghanistan. Ellsberg wasn't always considered a heroic figure — it took sustained, overwhelming dissatisfaction with the Vietnam War to make that happen.

"Ellsberg is also widely regarded as a hero today because history moved his way," Adam Cohen wrote in TIME. "The more it appears that what the NSA has been doing is wrong, the more Snowden will look like a whistleblower. History’s verdict on Snowden will turn on whether he got the balance right: Whether it turned out that we were more at risk of becoming a surveillance state than we were of terrorism."