At their summit meeting in Vienna in the spring of 1961, Khrushchev warned Kennedy that he would sign a treaty with East Germany restricting Western access to West Berlin. In response, Kennedy announced a major military buildup. In a television address to the nation on July 25, 1961, he described the embattled city as “the great testing place of Western courage and will” and declared that any attack on West Berlin would be viewed as an attack on the United States.

The speech had its desired effect. Khrushchev backed down from signing the treaty, even as thousands of East Germans continued crossing into West Berlin in search of freedom. In the early morning of August 13, 1961, the East German government, with Soviet support, sought to put this problem to rest, by building a wall of barbed wire across the heart of Berlin.

Tensions had abated slightly by the time Kennedy arrived for a state visit almost two years later. But the wall, an aesthetic and moral monstrosity now made mainly of concrete, remained. Deeply moved by the crowds that had welcomed him in Bonn and Frankfurt, JFK was overwhelmed by the throngs of West Berliners, who put a human face on an issue he had previously seen only in strategic terms. When he viewed the wall itself, and the barrenness of East Berlin on the other side, his expression turned grim.

Kennedy’s speechwriters had worked hard preparing a text for his speech, to be delivered in front of city hall. They sought to express solidarity with West Berlin’s plight without offending the Soviets, but striking that balance proved impossible. JFK was disappointed in the draft he was given. The American commandant in Berlin called the text “terrible,” and the president agreed.

So he fashioned a new speech on his own. Previously, Kennedy had said that in Roman times, no claim was grander than “I am a citizen of Rome.” For his Berlin speech, he had considered using the German equivalent, “I am a Berliner.”

Moments before taking the stage, during a respite in West Berlin Mayor Willy Brandt’s office, JFK jotted down a few words in Latin and—with a translator’s help—the German version, written phonetically: Ish bin ein Bearleener.

Afterward it would be suggested that Kennedy had got the translation wrong—that by using the article ein before the word Berliner, he had mistakenly called himself a jelly doughnut. In fact, Kennedy was correct. To state Ich bin Berliner would have suggested being born in Berlin, whereas adding the word ein implied being a Berliner in spirit. His audience understood that he meant to show his solidarity.

Emboldened by the moment and buoyed by the adoring crowd, he delivered one of the most inspiring speeches of his presidency. “Two thousand years ago, the proudest boast was ‘Civis Romanus sum,’ ” he proclaimed. “Today, in the world of freedom, the proudest boast is ‘Ich bin ein Berliner!’ ”