When the Clinton administration formulated the notion of rogue regime, they defined it as a country that embraced terrorism, was governed by an undemocratic cabal, and did not abide by the norms of diplomacy. Just how much of a rogue regime has Turkey become?

Under President Recep Tayyip Erdogan, Turkey’s turn toward terrorism is well-established. Turkey supports Hamas unabashedly , the al Qaeda-affiliated Nusra Front, and perhaps even the Islamic State . Ahmet Kavas, an Erdogan appointee, defended al Qaeda in the Islamic Maghreb while serving as ambassador to Chad. Recorded phone calls leaked to the press also suggest that Turkey may have armed Boko Haram in Nigeria.

What about diplomatic norms? Turkey is now practicing the same sort of hostage diplomacy in which North Korea and Iran engage. Last July, Sigmar Gabriel, at the time Germany’s foreign minister, called out Turkey for arresting German citizens as hostages to win diplomatic concessions or to force Germans to self-censor. “The cases of Peter Steudtner, Deniz Yucel and Ms. [Mesale] Tolu are examples of the absurd accusations of terror propaganda that obviously are only meant to serve to silence every critical voice in Turkey ... and also voices from Germany,” he said.

The Erdogan regime has also targeted Americans. Turkey detained and now seeks 35 years in prison for American pastor Andrew Brunson on terrorism charges even though it has been able to provide no evidence to support such assertions. Serkan Golge, a Turkish-American NASA scientist, now serves 7.5 years in prison on equally spurious charges. In addition, Turkey has arrested a number of local employees of American diplomatic missions in Turkey, violating the ability of the U.S. embassy and its various consulates to function. Erdogan has also leveraged Turkish organizations in the United States and Europe to spy on those deemed insufficiently loyal to the Turkish strongman.

Again, check the box on undemocratic cabals. Erdogan is an unrepentant strongman. He stands above the law, has embezzled billions, jailed journalists, and increasingly wields power with his immediate family to the detriment even of the political party he created.

The problem with rogue leaders is what they lack in governing capacity, they make up for in conspiracy and provocation. That appears increasingly to be the case with regard to Greece: Earlier this month, Turkey detained two Greek soldiers whom Turkish officials say strayed into Turkish territory while patrolling a forested border region in poor weather. The continued detention of the Greek soldiers comes amidst Erdogan’s ire that a Greek court refuses to release asylum-seeking Turks who fled to Greece against the backdrop of Erdogan’s 2016 purges of the Turkish military. The Greek court, for its part, refused to deport the Turkish soldiers after the Turkish government was repeatedly unable to provide credible evidence showing their culpability in the 2016 abortive coup. That Turks would seek refuge in Greece does not surprise given the deterioration in Turkish civil society; the rate of Turks seeking asylum in Greece has increased 40-fold in just three years.

Back to the two Greek soldiers whom Turkey now holds: Both Turkey and Greece quickly resolved past cases where Turks and Greeks strayed accidentally across their mutual border quickly at the local level, usually with communication among commanders along each zone of the border. This is what makes Turkey’s imprisonment of the Greeks a break with precedent. It is also impossible to dismiss the possibility that Turkey simply kidnapped the Greeks in much the same way that, in September 2014, Russian forces kidnapped an Estonian officer from within Estonia in order to pressure Russia’s smaller, Western-looking, and democratically-oriented neighbor.

The situation becomes even more worrisome given Turkey’s increasing revanchism toward former Ottoman territories now part of Greece, Bulgaria, Syria, and Iraq. Visiting Greece last December, Erdogan spoke about his desire to revise the 95-year-old Treaty of Lausanne, which established the borders of modern Turkey. And, on March 11, he referred to the southern Bulgarian town of Kardzhali as within Turkey’s “spiritual boundaries.” Turkish newspapers have published maps depicting the vision of ultranationalists and Erdogan with regard to expanded Turkey.

So what to do? As previous hostage diplomacy with Iran and North Korea shows, giving into demands or paying ransom only encourages more hostage-taking. Nor has appeasing Russia moderated Vladimir Putin’s behavior. To welcome any Turkish official in the United States or Europe so long as Turkey holds Americans and Germans hostage should also be a non-starter. The imprisonment of Greek soldiers in Turkey is further evidence that Turkey does not belong in NATO. Indeed, every NATO member in good standing should send Turkish officers home until Turkey releases its Greek hostages.

Proponents of engaging Turkey say that Erdogan is transactional and, if offered enough, will reverse course. Nonsense. NATO membership is meant to defend against crises, not to enable individual states to provoke them or initiate bidding wars to profit off them. Congress should go further. It should stop delivery of F-35s to Turkey or any other military or security assistance. So long as Erdogan remains in power, Turkey will remain a rogue regime deserving isolation and sanctioning, not partnership.

Michael Rubin (@Mrubin1971) is a contributor to the Washington Examiner's Beltway Confidential blog. He is a resident scholar at the American Enterprise Institute and a former Pentagon official.