On June 13, 1971, The New York Times began publishing a huge trove of top-secret documents disclosing that the U.S. government had systematically misled the American people about the American military intervention in Vietnam. The passing of this 30th anniversary provides a good opportunity to look back at the longest war in American history and the role of the Pentagon Papers in telling the truth about the conflict.

The immediate impact of the Papers was outrage and panic in the Nixon White House. Henry Kissinger, then the national security advisor, flew into a tantrum. President Nixon, shocked by the leak of the secret documents, ordered criminal prosecution of Daniel Ellsberg, the former Pentagon official, who had given the papers to The New York Times. And the Justice Department promptly sued the newspaper and obtained a temporary injunction that halted further publication. Mr. Ellsberg and a group of associates gave additional documents to a few other newspapers, which in turn were enjoined.

Prior restraint of publication raised a First Amendment issue. Regardless of how the Times and other newspapers had ob-tained the papers, could the government constitutionally halt the presses? The Supreme Court, in an expedited proceeding, held 6 to 3 that it could not. Publication continued until the entire collection of documents had been spread before the American people.

So much for the Nixon administration’s public response. Privately, it was determined to punish Ellsberg and anyone else connected with what it saw as a treasonous conspiracy. Mr. Nixon ordered creation of a secret agency, soon known as “the Plumbers,” to investigate leaks. One of its first moves was to break into the office of Mr. Ellsberg’s psychiatrist, in hopes of discrediting Mr. Ellsberg. Other break-ins and wiretaps quickly followed, including the burglary of Democratic Party headquarters in the Watergate office building. The first break-in tainted the case against Mr. Ellsberg, and the courts threw it out. The Watergate break-in and other desperate

acts by a panicked administration led eventually to impeachment proceedings against Mr. Nixon and his resignation in 1974.

The Pentagon Papers were the brainchild of Secretary of State Robert McNamara, a brilliant but troubled man. He found himself in the midst of President Lyndon Johnson’s escalation of what had started as a modest move to save South Vietnam from communism. France had abandoned the effort after a decisive military defeat, and American presidents, starting with Dwight D. Eisenhower, had quietly picked up where the French had left off.

As the United States involved itself deeper and deeper, Mr. McNamara orchestrated and supported the escalation on the one hand while privately expressing pain and misgivings. He ordered a collection of documents that would answer a long list of questions. Was the war actually progressing well, as officials kept claiming? Was the government telling the truth about American and Vietnamese casualties? Could the United States win the war? Were the armed services lying to their civilian leaders? Were the civilians lying to the American people?

The documents, never intended to become public, showed that the war actually was going poorly. Defeat was inevitable unless the United States raised the stakes, probably turning to nuclear weapons. That would have meant full-scale war with China. Gen. William Westmoreland’s claims of “light at the end of the tunnel” were false optimism, part of a hopeless effort to hold onto fading public support.

Mr. Ellsberg had hoped that the Pentagon Papers would awaken the American public and bring the war to a quick close. But that was too much to expect. Resistance to the war gradually increased, in and out of the government. Still, the leaders never could bring themselves to abandon the effort. It took four more years and 10,000 more American war dead before the U.S. forces were finally out, ending a conflict that was hopeless from the start.