As the editorial board at The Orange County Register recently put it, he was "a true American hero." 

They're right about Ellsberg. During the Vietnam War, through his release of the so-called Pentagon Papers in 1971, Ellsberg made public a large trove of secret government documents that exposed many of the Federal government's lies about its involvement throughout Indochina. Much of the information applied to the Johnson Administration which had been lying about the war to both the public and the Congress. Naturally, the release of this information, which smashed the Federal government's credibility on foreign policy, also called into question countless claims about the Nixon Administration. Nixon, of course, had already authorized an illegal and secret bombing campaign in Cambodia in 1969. 

At the time, the response to Ellsberg's deeds was hardly one of universal acclaim. Yet, over time, criticism has waned and Ellsberg's critics have been exposed for what they were: knee-jerk defenders of a regime devoted to war crimes and crimes against the Bill of Rights.