As a young man 30 years ago, I used to fear that the United Nations might in my lifetime pose a threat to the nation-state. A uniglobal, world-government movement that promised to abolish war might, I worried, destroy national sovereignty in the name of an amorphous appeal to “the brotherhood of man” or “our common humanity.”

Yet having attended last week’s Security Council Open Debate on universal peace (full title: “War, its lessons, and the search for a permanent peace”), I now realize that my fears were completely unfounded. The U.N. not only couldn’t organize universal peace; I suspect that the denizens of Turtle Bay don’t even really want it.

When the urbane, Cambridge-educated president of the Security Council, Prince Zeid Ra’ad Zeid Al Hussein of Jordan, called for a debate to mark the centenary of the outbreak of World War I, I doubt he expected that representatives of 58 countries, in addition to the 15 Security Council members, would want to speak. The debate’s stated aim was to try to learn from the catastrophe of 1914-18 and to see what the U.N. could do for international peace and stability before wars break out. Could history help?

“We speak in many meetings of the Security Council of the need for ‘dialogue and reconciliation’ with reference to a particular agenda item or other,” the prince said, “without in most cases knowing what we mean by it. And this is dangerous.” He came up with the imaginative idea of the U.N. sending squads of historians into former war zones with the peacekeepers, to work out why the conflict broke out. That way, a true narrative could be established before conflicting explanations contributed to spurring future conflict. The academics would be a kind of historians-sans-frontières team.

Rather than engage on that proposal or any ideas relating to World War I, though, the U.N. diplomats seemed mostly intent on using the occasion to prove that their nations were good and peace-loving—and that their opponents and neighbors were evil warmongers.

The Chinese ambassador started off this fabulously childish and unproductive process by stating that the Japanese premier, Shinzo Abe, recently visited the Yasukuni shrine in Tokyo “in order to pay tribute to those who launched the war of aggression and were soaked in the blood of the people of the countries that Japan invaded.” He added: “Mr. Abe’s tribute to those fascist war criminals is nothing less than a challenge to the victory against fascism.”

The South Koreans and North Koreans, who usually agree on nothing, jumped in with similar criticisms.

The German ambassador, while acknowledging his country started World War II, declined to admit any responsibility for its predecessor, saying that 1914 was all the fault of “outdated paradigms that could not keep up with the highly interlinked and rapidly changing world that was the young 20th century.” So that explains it.

The French ambassador’s speech was poetic in its references to the war dead, but he argued that history was no guide to the future anyhow. The British ambassador was the only speaker to admit to any wrongdoing by his country—for “Bloody Sunday” in 1972 in Northern Ireland—and quoted Prime Minister David Cameron saying “openness and frankness, however painful, do not make us weaker, they make us stronger.”

The Russian ambassador apparently wasn’t listening. He described World War II as “the victory of the Soviet Union-led anti-Hitlerite coalition,” a phrase that would have surprised Winston Churchill and Franklin Roosevelt. Getting in a dig against U.S. Ambassador to the United Nations Samantha Power, who had spoken powerfully about Syria, the Russian diplomat pointedly endorsed “the principle of nonintervention in the internal affairs of sovereign nations.” Somewhere Bashar Assad was smiling.

Russian hypocrisy was highlighted by the Georgian ambassador, who pointed out that the Putin government had built 50 kilometers of barbed-wire fences inside Georgian territory. “Ahead of the Olympic Winter Games in Sochi,” he explained, “the Russian Federation had expanded into a so-called security zone 11 kilometers deeper into Georgian territory.”

The centenary of World War I was used by the Armenian ambassador to accuse Turkey of being responsible for the genocide of 1.5 million Armenians after 1915, including “the brutal executions of the entire Armenian community in Anatolia. Deportations and killing were carried out. There were death marches into the deserts.” The Turkish ambassador bureaucratically replied that the deaths “do not fit into the definition of genocide that was set out in the 1948 Genocide Convention.”

The Rwandans and the Congolese also engaged in a bitter row over the events of 20 years ago in the massacres between the Hutus and Tutsis and their aftermath.

The most powerful of all the speeches was delivered by the Israeli ambassador, Ron Prosor, who spoke of his father’s escape from Nazi Germany. “In the last century,” he said, “this pattern of defamation, degradation and bloodshed has been the hallmark of an impending atrocity. Despite the pledges—even in this chamber—of ‘never again,’ we have seen the pattern repeat itself over and over again.”

To judge by the United Nations’ treatment of the opportunity for an intelligent and enlightening debate about the lessons of war, the pattern isn’t going to change anytime soon. I no longer fear the danger of world government—or hold out much hope for universal peace—after seeing the way the world behaves when it’s talking to itself.

Mr. Roberts is a historian whose next book, “Napoleon: A Life,” will be published by Penguin in November.