Can Dundar, the former editor in chief of the leading Turkish newspaper Cumhuriyet, is now living in exile.

Earlier this week, amid burgeoning scandals in Washington and a dramatic shift in the balance of power in Syria, President Trump revealed a letter he had sent to the president of Turkey. Trump was apparently trying to show a confused American public that he’s really the man in charge.

Trump was acting on impulse. Yet his decision is likely to haunt Turkish-U.S. relations for a long time to come.

The text of the letter rocked Turkish politics. “Don’t be a fool!” Trump admonished his Turkish counterpart, Recep Tayyip Erdogan — an astonishing insult to a man who carefully guards his public image as a strongman. Trump threatened “to destroy the Turkish economy” and reminded Erdogan that “I have worked hard to solve some of your problems,” a reference to some personal matter whose nature we can only guess at. And he also recommended that Erdogan negotiate with Syrian Kurdish leader Gen. Mazloum Abdi — a man that Turkey considers to be a terrorist.

For anyone to address Erdogan in such language inside Turkey is inconceivable; he has sent many people to jail for far milder comments. He also has a long record of reacting harshly to criticism from abroad, and commentators waited with bated breath to see how he would respond.

At first, however, the Erdogan administration pretended not to have received the letter — leaving others to register their reactions. A spokesman for the main opposition party issued a withering statement: “The Republic of Turkey has never accepted such arrogance,” said Faik Oztrak of the Republican People’s Party, who referred to the letter as a “rag.” Former prime minister Ahmet Davutoglu tweeted: “The Turkish nation has been insulted. [Erdogan’s planned] U.S. visit must be canceled unless an immediate apology is forthcoming.”

As the outcry grew, Erdogan’s camp soon felt compelled to come to his defense. “Erdogan rejected the offer of mediation [with the Syrian Kurds] and it was thrown into the trash,” a government source told local media. The same source claimed that Turkey’s operation of northern Syria was “the clearest answer” to the letter from the U.S. president.

Yet to assume that the affair ends there would a grave mistake. For the historically minded, Trump’s missive recalls another letter sent to Ankara from Washington 55 years earlier. In 1964, Turkey’s apparent preparations for a military operation in Cyprus unnerved President Lyndon B. Johnson. Johnson wrote to Turkish Prime Minister Ismet Inonu, expressing grave concern about the risk of a Turkish-Greek war in the Mediterranean and the damage it could cause to NATO. Johnson also warned about the possibility of direct involvement by the Soviet Union. In such a case, he said, the United States would not be able to defend Turkey — nor would he agree to the use of American military equipment.

The “Johnson letter” of 1964 was a turning point in Turkey’s relations with the United States. Ankara refrained from acting against Cyprus for the time being, but Turkish leaders never forgot how a U.S. president had lectured them. Four months later, Inonu dispatched his foreign minister to Moscow, seeking to restore relations with its northern neighbor after a quarter century of hostility. This diplomatic gambit was a direct result of Johnson’s letter.

The similarities do not end there: public reaction to the Johnson letter also lit the fuse of an intense spate of mostly left-wing anti-Americanism that would peak in 1968, fanned by indignation over the Vietnam War and western “imperialism.”

Trump’s letter is almost certain to have a comparable effect. America’s popularity among Turks had been on a downward slope well before Trump’s letter, at any rate. When pollsters asked Turks to name the countries that pose the greatest threat to Turkey three years ago, 44 percent of them picked the United States; this year the figure reached 81 percent.

When Erdogan finally deigned to meet with Vice President Pence, just 24 hours after he had said he would not, pro-government media played down the concession. Erdogan’s critics charged that the Turkish president had succumbed to Trump’s advice not to “be a tough guy.” Erdogan will be determined to have the last word on the subject. On Friday, he said that he “cannot forget” the letter from his American counterpart, hinting darkly that his country would “do what’s necessary” in response “when the time comes.”

Trump’s letter could easily foment anti-American feeling in Turkey just as Johnson’s letter did more than half a century ago. And just like Inonu, Erdogan may respond by tilting further towards Moscow.

This particular bit of history also holds a warning, too, though. Students of history know all too well that the Inonu cabinet fell eight months after Johnson’s letter.

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