The United States has been openly arming the Syrian Kurdish fighters in the war against ISIL since May 2017. Following the start of the Turkish invasion of northern Syria aimed at ousting US-backed Syrian Kurds from the enclave of Afrin, Mattis said in January 2018: "Turkey is a NATO ally. It's the only NATO country with an active insurgency inside its borders. And Turkey has legitimate security concerns." Turkish Deputy Prime Minister Bekir Bozdağ urged the United States to halt its support for Kurdish YPG fighters, saying: "Those who support the terrorist organization will become a target in this battle."