This article is part of a special report on the 50th anniversary of the Pentagon Papers.

The Pentagon Papers may have been all over the front pages of U.S. newspapers 50 years ago, but they were barely noticed in Hanoi. Communist leaders were too busy fighting their war in the present to look at its history.

Besides, the contents of the papers only served to confirm their longstanding notions.

By the time “Vietnam Archive: Pentagon Study Traces Three Decades of Growing U.S. Involvement” appeared on the front page of The New York Times on June 13, 1971, the North Vietnamese government had been claiming for years that American military involvement was illegitimate.

“What shocked Americans at the time was nothing new to the Vietnamese,” said Dr. Vu Minh Hoang, a historian at Fulbright University Vietnam in Ho Chi Minh City.

Not until August of 1971 — and then buried on page six by the Vietnam News Agency — did the state-run media finally see fit to report the news.

That would change dramatically in the decades that followed.

This little-noticed report would go on to have a seismic impact in Vietnam — fortifying the country’s military and public with evidence that their cause had been just. It supplied an exhaustive accounting of the U.S. prosecution of the war, which helped shape Vietnam’s own history and sense of identity for decades.

The saying goes that history is written by the victors, but in the case of the Vietnam War, the losing side has held sway over the narrative. And the Pentagon Papers — even as they narrate the United States’ own defeat almost in real time — have become a key piece of that sway. Since the Communist Party of Vietnam has been steadfast in its refusal to release its own unvarnished accounting of the war, Vietnamese historians have far less to use in writing their own histories. And thus far, no Vietnamese counterpart to Daniel Ellsberg has emerged to leak such documents.

With Mr. Ellsberg’s leak, rather than having to wait decades for declassification, scholars on both sides of the Pacific could analyze U.S. policy in Vietnam before the archival dust could accumulate.

After war’s end, the very first Communist Party-approved histories of the war published in Hanoi copiously cited the Pentagon Papers in their footnotes. From these early histories to the current versions, the argument has remained consistent: According to the U.S. government’s own internal study, America had no right to get involved and no means to win the war once it did.