‘I believe that this historic visit will be a new turning point in the relations of Turkey and Israel. Our common goal is to revitalize political dialogue between our countries based on common interests and respect for mutual sensitivities.’

That was President Erdogan of Turkey back in March 2022, when President Herzog of Israel visited Ankara after 12 years of icy relations. The “turning point” was celebrated around the world. No longer. Today Mr. Erdogan drove a final nail in the coffin of one of history’s shortest honeymoons. “We, as the Republic of Turkey and its government, have currently severed all relations with Israel,” the mercurial neo-Ottoman president told reporters today. 

Could it be that the Turkish strongman is being swayed by influencers like Greta Thunberg? On Sunday the Swedish activist issued “an urgent call to action” on X, urging her followers to protest in front of Turkish embassies around the world. “President Erdogan talks of solidarity with Palestine, but Turkey’s ports remain open, allowing oil to flow to Israel, fuel for the very machinery slaughtering Palestinians,” she said.

Melding climate activism with antisemitism has never sounded this profound. So a small number of protesters screamed on Monday even in front of the Turkish mission to the United Nations at New York’s First Avenue. Their beef seemed to be with a man who, while hosting top Hamas leaders in Turkey for more than a decade, is too easy in their eyes on the hated Jews and Zionists. Yet is Mr. Erdogan simply heeding their vox popoli? 

In reality, the Turkish Islamist has long played a double game. Mr. Erdogan champions Mideast militants and terrorists while he shuns moderate Arabs. The Palestinian Authority, backed by America and Europeans, is his nemesis. Hamas is an ally. At the same time the Ankara pasha often highlights the benefits of Turkey’s relationship with Israel, as he did in 2022 by hosting Mr. Herzog amid pomp and circumstance. 

While visiting New York in 2003, shortly after Mr. Erdogan’s Islamist party, known as the AKP, won the election that made him prime minister, the new leader told our Benny Avni in an interview that his top wish is to cultivate relations with Israel. After that, things went downhill fast, hitting a nadir in 2010, when the Israeli navy intercepted Islamists intent on violating Israel’s sovereignty as they feigned “aid” delivery to Gazans on the Mavi Marmara.

Even while Mr. Erdogan raised cane over the incident, a delegation of Turkish government officials nevertheless visited Israel to seal an arms-purchasing deal. Then, after cool heads prevailed and Mr. Erdogan lowered his vitriol level, Israeli vacationers became enamored of discounted trips to Turkish resorts. Entrepreneurs at Istanbul created whole industries catering exclusively to Israeli markets. All was well on the Turkish front. 

The love affair cooled off after October 7, 2023, when Ankara turned on Israel ere it had a minute to mourn victims of a massacre committed by Mr. Erdogan’s cronies in Hamas. Israelis boycotted Turkish tomato imports; Ankara cut trade. Through the ups and downs, Turkey’s relations with Israel were beneficial to both countries, while ties between Hamas and Turkey contributed nothing. They are driven only by Mr. Erdogan’s ideological zeal. 

Note to President Trump then, as he reshapes policies: This is not business, it’s personal. The heart of a North Atlantic Treaty ally who craves good relations with Washington is bleeding for antisemitic groups that are decisively hostile to America. We have leverage, including denying Mr. Erdogan arms, or even relocating the air base at Turkey’s Incirlik. It’s time to bring into line a wayward member of the North Atlantic Treaty.