President Trump and French President Emmanuel Macron during a Bastille Day parade in Paris in July 2017. (Carolyn Kaster/AP)

Correction, Nov. 10:  This piece originally misstated the number of fatalities in World War I as 40 million. The piece has been revised.

I am still haunted by my visit 14 years ago to the World War I battlefields of France, from Verdun to the Somme. All those long, neat rows of graves — all those young men struck down in a senseless, inconclusive conflict that claimed 20 million lives. Particularly heartbreaking were the markers commemorating “Soldat Inconnu, Mort Pour la France” (an unknown soldier who died for France) — someone whose identity has been erased from history.

I pray — with no expectation that my prayer will be answered — that President Trump will pause during his visit to France this weekend for the 100th anniversary of the end of World War I to contemplate what happened and why. He will have a chance for some sober reflection, if he is capable of it, when he visits the American war cemeteries at Aisne-Marne and Suresnes. But it does not augur well that he will skip President Emmanuel Macron’s Paris Peace Forum, designed to bring together leaders to foster international cooperation.

Macron has been clear-eyed about what caused the Great War: “the leprosy of nationalism.” He warns that the danger of another catastrophe is rising because nationalism has been loosed on the world once again. “The world is fracturing, new disorders are appearing and Europe is tipping almost everywhere toward extremes and again is giving way to nationalism,” Macron said in a televised address. “Those who do not see what is going on around us are sleepwalking. Not me.”

His choice of word — “sleepwalking” — is significant because one of the best new histories of the outbreak of World War I, by the Cambridge University historian Christopher Clark, is called “The Sleepwalkers: How Europe Went to War in 1914.” One cannot help thinking of the present day when Clark writes of “monarchs and statesmen” such as Kaiser Wilhelm II who “were positively obsessive about the press and spent hours each day poring through cuttings.” Sound like anyone we know? So, too, we can hear contemporary echoes when Clark describes “aggressive ultranationalist organizations whose voices could be heard in all the European capitals,” even though they “represented small, extremist constituencies.” Their aggressive ideology was the kindling that ignited when Archduke Franz Ferdinand was assassinated.

There are similar ultranationalist organizations today, and their constituencies are no longer so small. They include the Law and Justice party (the ruling party in Poland), Jobbik (the ruling party in Hungary), United Russia (the ruling party in Russia), the League (one of the ruling parties in Italy), the Freedom Party (one of the ruling parties in Austria), the Alternative for Germany (Germany’s second-most popular party) and the National Rally in France (which is ahead of Macron’s party in a recent poll for European Parliament elections). They are all promoting the kind of nativism and nationalism that was widespread in Europe before World Wars I and II.

After 1945, the United States tried to curb the forces of nationalism and encourage international cooperation. President Harry S. Truman, who as a captain in the field artillery served in France in 1918, summed up the American achievement in his 1953 Farewell Address: “After the First World War we withdrew from world affairs — we failed to act in concert with other peoples against aggression — we helped to kill the League of Nations — and we built up tariff barriers that strangled world trade. This time, we avoided those mistakes. We helped to found and sustain the United Nations. We have welded alliances that include the greater part of the free world. And we have gone ahead with other free countries to help build their economies and link us all together in a healthy world trade.”

Unlike Truman, Trump knows nothing of war or of history. (He has played golf at least 159 times since taking office but never once visited U.S. troops in Iraq, Afghanistan or Syria.) Proving George Santayana’s maxim that “those who cannot remember the past are condemned to repeat it,” he appears bent on repeating the very mistakes Truman warned about.

Trump has launched trade wars. He has pulled out of one international obligation after another — the Trans-Pacific Partnership, effectively the Paris climate accord, the Iran nuclear deal, even the Universal Postal Union. He has denigrated the United States’ allies and questioned the value of its alliances. (And he did it again on Friday.) He has praised strongmen such as Recep Tayyip Erdogan, Xi Jinping and Abdel Fatah al-Sissi for undermining democracy in their own countries. He has described his foreign policy as “America First,” after the isolationist movement of the 1930s and proudly embraced the mantle of “nationalism,” oblivious (or perhaps not?) to its dark connotations. He has undermined the rule of law internationally and domestically — witness his designation of a political hack to be acting attorney general despite his lack of Senate confirmation. And, most despicable of all, he has employed racism and xenophobia — prejudices all too prevalent in 1914 — as political tools.

The world would greatly benefit if Trump could reflect for even a second this weekend about where such unbridled and unprincipled displays of power can lead. But to expect self-reflection from this president is as far-fetched as to expect him to sit down at a piano and play a Mozart sonata — something that Truman did for an audience of 30 million Americans.