In the days just before Turkey’s military incursion into Syria, for which the stated aim includes purging a Kurdish militia that has been allied with the United States in the fight against the Islamic State, President Trump made a comment on the history of the two conflicting sides. He defined Kurds as Turkey’s “natural enemy,” adding, “one historian said they’ve been fighting for hundreds of years.”

I am not sure who that historian was, but as someone who has studied this particular history, I can assure you that the tension between Turks and Kurds is not centuries old. It is actually about one century old, and it’s the result of a very modern force: nationalism.

The history does begin in the early 16th century, when the Ottoman Empire, founded in western Anatolia by Sunni Turks, began to expand eastward, only to conflict with the Shiite Safavid Empire in Persia. The Kurds, a tribal people, most of whom were Sunni Muslims, were caught in the middle; soon they willingly joined the Ottomans. Through the next four centuries, they lived under the same state with Turks, Arabs, Bosnians, Armenians, Greeks and Jews — because the Ottoman Empire, like the neighboring Hapsburg Empire, was a multiethnic and multireligious mosaic.

The Ottoman elite was mostly Turkish, but not Turkish nationalist. So Kurds never faced any denial of their identity. Their ancestral homeland was often called “Kurdistan,” which even briefly became the name of an administrative region in the 19th century. In the same era, there were a few revolts by Kurdish chieftains, but only as a reaction to the centralization of the state and the new taxes and obligations it entailed.