Case in point: Turkish President Recep Tayyip Erdogan. Trump ran for president by pledging to wage war on “radical Islam,” yet he has granted concessions to Erdogan that his advisers told him are inimical to U.S. national security interests. In a phone call with Erdogan on Oct. 6, Trump agreed to pull U.S. troops from the Syrian-Turkish border, clearing the way for Turkish troops and a motley crew of Islamist proxies to assault the Kurdish-led Syrian Democratic Forces, which partnered with the United States to defeat the Islamic State in Syria.

Trump was apparently counting on Erdogan not to do anything the United States would “consider to be off limits.” Three days later, after the Turks’ unrestrained assault had begun, Trump pleaded with Erdogan, “History will look upon you favorably if you get this done the right and humane way.” If Trump had been more skeptical, he would have discovered that Erdogan’s ideology entails the rejection of limits that would otherwise constrain a NATO ally like Turkey.

In contrast to Islam, the faith practiced by more than a billion Muslims, Islamism is a political doctrine that calls for the subordination of governments and peoples to Islamic law. In pursuit of that goal, Erdogan has supported the violent jihad of Hamas and even, for a while, Jabhat Fatah al-Sham, or the Nusra Front, an al-Qaeda affiliate in Syria. He has also given free rein to terror financiers, helped Iran evade sanctions and taken American citizens as hostages.

Erdogan’s Justice and Development Party (AKP) rose to power in 2002 on the heels of an economic crisis that pushed all existing political parties out of the Turkish parliament. Erdogan, who presented himself as an outsider capable of fixing a broken system, reassured skeptics wary of his radical past by claiming that he had “taken off the shirt” of Islamism to establish a “conservative democratic party.” In fact, the AKP’s roots, like those of the long line of Turkish Islamist parties before it, are intertwined with those of the Muslim Brotherhood, the region’s preeminent advocate of Islamism since its founding in Egypt in 1928.