Ben H. Bagdikian, who had a key role at The Washington Post in the publishing of the Pentagon Papers and later became a prominent media critic and educator. (Courtesy of Ted Streshinsky)

During his tenure as national editor of The Washington Post in the early 1970s, Ben H. Bagdikian embarked on two secret missions under very different circumstances. First, he obtained the Pentagon Papers for The Post, physically delivering them to the home of then-editor Benjamin C. Bradlee.

The publication of the papers ultimately resulted in a landmark Supreme Court decision concerning freedom of the press.

Months later, Mr. Bagdikian went under cover in a ­maximum-security prison, passing himself off as a murderer for a Post investigative series.

Mr. Bagdikian, who went on to become an influential educator, author and media critic, warning of the dangers of concentrated ownership of news organizations, died March 11 at his home in Berkeley, Calif. He was 96.

His wife, Marlene Griffith Bagdikian, confirmed the death but did not specify a cause.

In June 1971, Mr. Bagdikian, who held the title of assistant managing editor for national news, received a phone call asking him to travel to Boston for a clandestine meeting.

The call came days after the New York Times had published excerpts from the Pentagon Papers, a secret history of U.S. involvement in Vietnam. A federal judge then ordered the Times to stop publishing the papers for reasons of national security.

The Times had received papers from Daniel Ellsberg, a onetime defense analyst Mr. Bagdikian had met several years before in California.

Mr. Bagdikian, who was told to bring an empty suitcase with him, learned that Ellsberg would meet him in Boston and turn over additional documents from the Pentagon Papers.

The suitcase was not big enough, and Mr. Bagdikian filled cardboard boxes with the pages Ellsberg handed over. He flew back to Washington with the papers sitting on the seat next to him.

Bradlee recalled in a speech several years later the moment when “silver-haired Ben Bagdikian, his shoulders bending under the burden of two heavy cartons, staggered up the stairs of my house . . . and dropped the Pentagon Papers on my living room floor.”

Mr. Bagdikian was among the editors and reporters who reviewed more than 4,000 jumbled pages, as members of the The Post’s news and legal staffs weighed the consequences of publishing the papers.

Mr. Bagdikian was one of the strongest voices in favor of publication, arguing that the government could not use the cloak of “national security” to limit what newspapers could print. He uttered a line that neatly summed up the principle involved: ‘The only way to assert the right to publish is to publish.”

“Bradlee had never admired Bagdikian more,” David Halberstam wrote in his 1979 book about the media, “The Powers That Be.”

After The Post published the papers, Bradlee received a telephone call from a Justice Department official — future Chief Justice William H. Rehnquist — threatening to prosecute the paper for espionage unless it agreed not to print any more of the Pentagon Papers.

“We must respectfully decline,” Bradlee said.

The Post joined the Times in a legal battle that, because of its national importance, reached the U.S. Supreme Court within days. The court ruled, 6 to 3, that the government could not impose “prior restraint” on the newspapers to block publication of the Pentagon Papers. It is considered one of the most significant decisions supporting the First Amendment right to freedom of the press.

Several months after the Pentagon Papers, Mr. Bagdikian led a Post investigation of conditions in U.S. prisons. For one harrowing first-person story, he went under cover purporting to be a murderer in order to observe prison life from the inside.

He originally planned to enter a prison in Oklahoma until an ex-convict warned him, “You’ll never get out alive.”

Instead, Mr. Bagdikian approached the attorney general of Pennsylvania, who agreed to allow him to enter Huntingdon State Correctional Institution without the knowledge of anyone else at the prison. He was Prisoner No. 50061.

“I was in a maximum security penitentiary for murder,” Mr. Bagdikian wrote in The Post on Jan. 31, 1972. “But I hadn’t killed anyone. No one at the prison — warden, guards, inmates — knew that. All they knew was that one night, two state policemen delivered me in handcuffs as a ‘transfer’ from a distant county jail.”

Mr. Bagdikian spent six days in the prison. He was removed after one inmate began to suspect something unusual about him and pointedly asked, “You here for your health?”

In his story, Mr. Bagdikian described widespread racial tension behind bars, outbursts of violence, open “homosexualism” and an elaborate, yet fragile, code of etiquette.

“You enjoy the trust of others but at the same time fear it,” he wrote. “Everyone is trapped together and each man has the power to harm the others.”

He and Post reporter Leon Dash published their eight-part series as a book, which Mr. Bagdikian later expanded into another book, “Caged: Eight Prisoners and Their Keepers” (1976).

After his undercover experience, Mr. Bagdikian was approached by Bradlee.

“I’ve got to hand it to you, buddy,” Bradlee said. “You’ve really got big ones.”

Ben-Hur Haig Bagdikian was born Jan. 30, 1920, in a town then known as Marash in present-day Turkey. His Armenian family soon fled the country to avoid persecution.

During the escape, Mr. Bagdikian, then an infant, was dropped in the snow. He was feared dead until he began to cry.

The family settled in Stoneham, Mass., where his father was a Protestant pastor.

After graduating from Clark University in Worcester, Mass., in 1941, Mr. Bagdikian began his newspaper career in Springfield, Mass.

He was an Army Air Forces officer during World War II, then worked briefly in New York before joining the Providence Journal in 1947.

He was part of a team that won a Pulitzer Prize in 1953 for coverage of a bank robbery and also served as a Washington reporter and foreign correspondent. In the 1960s, he was a Washington-based correspondent for the weekly Saturday Evening Post and published his first book, about poverty in America, in 1964.

He met Ellsberg in the late 1960s while working on a media study at the Rand Corp. in California. He came to The Post in 1970.

Throughout his career, Mr. Bagdikian was preoccupied with the ethics of the news business, and he won a Peabody Award in 1951 for articles analyzing the content of commentators such as Drew Pearson and Walter Winchell.

As early as 1957, Mr. Bagdikian called for newspapers to hire in-house critics, or ombudsmen, to address public concerns about journalistic practices. In 1972, he became The Post’s second ombudsman. As a conduit of outside and internal complaints, he began to clash with Bradlee, and after several months Mr. Bagdikian left the paper.

He held several interim posts, including a stint at American University, and wrote widely before joining the faculty of the University of California at Berkeley in 1976. He later became dean of its Graduate School of Journalism.

In his role as a media critic, Mr. Bagdikian said reporters were too often limited by their publishers’ financial interests and lack of imagination.

“Trying to be a first-rate reporter on the average American newspaper,” Mr. Bagdikian wrote in Esquire magazine in 1967, “is like trying to play Bach’s ‘Saint Matthew Passion’ on a ukulele.”

In 1983, he published “The Media Monopoly,” a study of the growing concentration of news outlets in the hands of a few large conglomerates. The book helped inspire a variety of watchdog groups and reform efforts.

“As a media critic,” Fordham University professor Arthur S. Hayes wrote in “Press Critics Are the Fifth Estate” (2008), “Bagdikian has been farsighted, inspirational, influential, long lasting, and a forerunner.”

Mr. Bagdikian retired from the University of California in 1990 but remained an active voice on media issues for many years. He revised “The Media Monopoly” in 2004 as “The New Media Monopoly,” noting that the 50 large media companies cited in the first edition of his book had dwindled to five.

His marriages to Elizabeth Ogasapian and former Post reporter Betty Medsger ended in divorce.

Survivors include his wife of 32 years, Marlene Griffith Bagdikian of Berkeley; and a son from his first marriage, Eric Bagdikian of Longmont, Colo. Another son from his first marriage, Christopher Bagdikian, died in 2015.

In a 1995 memoir, “Double Vision: Reflections on My Heritage, Life, and Profession,” Mr. Bagdikian described his narrow escape from Turkey as a child and the joys and difficulties of his many years in journalism.

“If I were choosing my life work all over again, would I be a reporter?” he wrote. “You bet I would.”