If, on January 1, 2022, had there been predictions that the Financial Times’s and Time magazine’s “Person of the Year” would be a 43-year-old Jewish comedian from Ukraine, who would have believed it?

One year into Vladimir Putin’s invasion of Ukraine, Volodymyr Zelensky has become a global hero. Ukrainians are hailed for their courage and sense of nationhood. A half-century ago, most people abroad and many of those living in Ukraine called the residents there “Russians” living in just another province of the Union of Soviet Socialist Republics.

There can be surprises in history. The Helsinki Accords of 1975 are one, and that is why I have written a book called Would You Believe … the Helsinki Accords Changed the World?: Advancing Global Human Rights and, for Decades, European Security.

On August 1, 1975, 35 heads of state from Europe, the United States, and Canada met in the Finnish capital to sign the Final Act, the concluding document of the Conference on Security and Cooperation in Europe (C.S.C.E.) and the product of two years of negotiations.

The United States was represented by President Gerald R. Ford, an unelected leader destined to lose his office the following year. The Kremlin was represented by Communist Party general secretary Leonid Brezhnev, who suffered a stroke a few months later but carried on, mumbling and confused, until he died, in 1982.

And on December 25, 1991, the U.S.S.R. itself disappeared.

Reaction to the Helsinki Accords was notable for declarations of their insignificance. The Wall Street Journal editorial page and the New York Times columnist William Safire urged Ford not even to go to Helsinki.

And yet, in 2023 the case can be made that the Final Act did provide decades of European security and launched the human-rights movement that has become a significant political factor in the world.

One year into Vladimir Putin’s invasion of Ukraine, Volodymyr Zelensky has become a global hero. There can be surprises in history.

I have peculiarly unique credentials for telling this story. As the Moscow correspondent for The Washington Post in 1975, I was one of the few reporters who ever wrote about the C.S.C.E. My father-in-law, Albert W. Sherer Jr., the U.S. ambassador to Czechoslovakia, was the head of the American delegation in the talks. After the summit, a Moscow-based Helsinki monitoring group was established, and I knew every one of its members.

When the New York–based organization Helsinki Watch was created, in 1978, I knew all the founders. My wife, Susan, later became that group’s first press director, and, after moving from journalism to book publishing, I served for years as a member of the board of what became known as Human Rights Watch, the world’s leading NGO on these matters.

The book describes how the Moscow and New York Helsinki Watch groups became Human Rights Watch, the international enterprise that made monitoring and advocacy important in world affairs as it never had been before.

Here briefly is a measure of the impact of the Helsinki Accords over the decades: When the Accords were signed, in 1975, détente was the tenor of East-West relations, with the United States and the Soviet Union lessening tensions in, for example, the nuclear-arms race. The Cold War reheated in the 1980s, but then Mikhail Gorbachev led the Soviets through an almost bloodless revolution.

In Europe, the Helsinki Accords defined the terms for re-unification of Germany’s two halves. The Soviets were persuaded to accept that possibility and provisions for human rights in the Final Act in order to get overall recognition of the imperial borders they most wanted. Shortly thereafter, the Common Market became the European Union, the Continent’s economic alliance, while Yugoslavia imploded in the Balkan wars of the 1990s. But the wars in Bosnia and Kosovo never spread beyond what had been Yugoslavia’s borders.

In the post-Soviet era, Russia made military incursions on its periphery, in Georgia and elsewhere. Russia then went after Crimea and the Donbas, two parts of Ukraine with indisputably close ties to Russia. And then, on February 24, 2022, Russia launched all-out war against Ukraine, the first cross-border aggression in Europe since World War II. The Helsinki era was over.

Diplomacy by its nature does not provide colorful narratives. There is a journalism cliché: “Dog bites man” is routine, but “man bites dog” is news. This is why I believe readers will find the story of the Helsinki Accords and their aftermath worth their time.

Peter Osnos and Holly Cartner’s Would You Believe … the Helsinki Accords Changed the World?: Human Rights and, for Decades, Security in Europe will be published on March 22 by Platform Books