Newton N. Minow, senior counsel at the law firm Sidley Austin, was a member of the Rand Corp. board for 30 years, serving as chairman from 1971 to 1975.

"The Post," the new Steven Spielberg film starring Meryl Streep as former Post publisher Katharine Graham and Tom Hanks as the paper's editor, Benjamin C. Bradlee, is one of the best movies of the year. I had a front-row seat to a back story for the film.

The film is about a great constitutional crisis of the 1970s — the Nixon administration's effort to stop newspapers from publishing top-secret military records known as the Pentagon Papers. President Richard M. Nixon claimed that publication would threaten national security and took the case all the way to the Supreme Court, where, in a 6-to-3 decision , the justices ruled that under the First Amendment the government could not stop The Post from publishing materials leaked by an employee of the Rand Corp.

I had been chairman of the board at Rand for only a few weeks when the corporation's president called me to say that a Rand employee, Daniel Ellsberg, was responsible for leaking the Pentagon Papers. The leaked documents, intended for future historians, revealed decades of deception from at least three presidents and their defense secretaries about our efforts in Vietnam.

The leak threatened the credibility and reputation of Rand, a highly respected not-for-profit think tank. The Defense Department immediately announced that it was canceling Rand's security clearance, which could have shut it down.

I immediately went to Washington to see then-Deputy Defense Secretary David Packard. I told him I brought greetings from my fellow Rand trustee, Bill Hewlett. The two men had co-founded Hewlett-Packard in a one-car garage in Palo Alto, Calif., and it went on to become one of the world's leading technology companies. Packard perked up.

"How is Bill?" I told him that Bill was not so good because the Defense Department had taken away Rand's security clearance. I then told him that I intended to hold a news conference the next morning to explain that Ellsberg was at Rand because the Defense Department sent him there with the top-secret clearance it had given him.

After conferring with his lawyer, Packard disclosed that the department rescinded the security clearance on the direct orders of the president, and he asked for a few days to renew it. I canceled my news conference. Packard kept his word, and Rand continues to provide the government with nonpartisan, independent analysis four decades later.

"The Post" shows the paper's struggle with its own conscience over publishing after Nixon's Justice Department got an injunction preventing the New York Times from writing any more articles based on the Pentagon Papers. And it shows the care that both the Times and The Post took to make sure the revelations in the documents Ellsberg leaked were presented in context and without putting any troops at risk. I knew both Graham and Bradlee, who were patriots, and I knew they would never hurt the country they loved.

This soul searching over a leak is hard to imagine in a world where Donald Trump, as a presidential candidate, spoke of his "love" for WikiLeaks; where "rogue" accounts inside federal agencies post tweets contrary to official statements; where Chelsea Manning leaked hundreds of thousands of classified and sensitive documents, made available on the Internet, without any vetting by journalists.

The size of today's leaks is orders of magnitude greater than Ellsberg's 47 volumes. It took him weeks to photocopy them a page at a time. Today, people can carry thumb drives — as Edward Snowden did — with thousands of pages out of the buildings in their pockets. Today, also, more is labeled secret than ever before, and we have a president who, unlike his predecessors, will not release his tax forms or visitor logs.

"The Post" contains important reminders about the vital role that a highly professional, fair-minded press can play in a democracy. It is also a reminder that no matter what kinds of protections are put in place, secrets will come out; it's just a question of when and how embarrassing they will be, and whether we will have trustworthy intermediaries who know the difference between secrets that are essential for national security and secrets that must be revealed for the public interest. It is an important film that is especially significant for young people who did not live through the period of the Pentagon Papers and for those in office today who have forgotten its lessons.

There will always be tension between the government's need for secrecy, the public's wish for both privacy for themselves and transparency for everyone else, and the need for accountability that is only possible with disclosure. Tom Hanks has said he would not participate in a screening of the film in the White House. Tom, with all respect to you, my favorite actor, I think it is Trump, more than anyone else, who needs to learn the lessons of this film.