There’s a crucial, overlooked aspect of Daniel Ellsberg’s legacy that’s very much worth saluting—his transformation from a believer in the Vietnam War to a horrified opponent of it.

Ellsberg, who died on June 16 at age 92, had been part of the military-industrial establishment in the 1960s—a smart young man working as a Pentagon consultant at the Rand Corporation think tank. In the mid-’60s, he wound up spending two years in Vietnam, on a mission for the State Department to study counterinsurgency. He traveled through most of the country, witnessing not simply the war up close but Vietnam itself, and the people who lived there.

A few things became obvious. Despite then-President Richard Nixon’s commitment to “winning” the war— and continuing America’s tradition of greatness—“there was no prospect of progress of any kind,” Ellsberg told The Guardian, “so the war should not be continued.”

The war was no longer an abstraction to Ellsberg. It was hell visited upon humanity. Now what? As of 1969, he had 7,000 pages of documents in his safe which indicated that president after president after president knew the war was absurd and unwinnable.

Ellsberg decided to act. He spent eight months secretly copying his document trove, eventually releasing the papers to The New York Times, which defied Nixon’s orders that the contents were a national security risk and must not be published.

It wasn’t simply the Pentagon Papers themselves but also Ellsberg’s transformation—his awareness that the harm the war was doing, the innocent people it was killing, the unending hell it was creating, mattered. “Vietnam became very real to me,” he said. In other words, war is not an abstraction. This truth sits in the collective human soul.

As one vet described what his training taught him: “The enemy is not a human being. He has no mother or father, no sister or brother.”

No, he’s just in the way. The whole planet’s in the way.

Robert Koehler is a Chicago award-winning journalist and editor. He is the author of ‘Courage Grows Strong at the Wound.’