Turkey’s President Recep Tayyip Erdogan threatened to close the Incirlik air base after U.S. politicians threatened Ankara with sanctions. Last week, the U.S. Senate passed a resolution, recognizing the mass killing of Armenians by the Ottoman Empire as a genocide.

The U.S. Air Force has flown combat sorties from Incirlik and stores nuclear warheads there. It is located in Southern Turkey around 150 kilometers from the Syrian border. During the first Gulf War the U.S. Air Force launched bombing missions against Iraq from Incirlik. After the 9/11 attacks, the U.S. Air Force started piloting drone missions against ISIL from the base.

The mass killings and expulsions of around 1.5 million Armenians by the Ottoman Empire began in 1914-15 and continued through 1923. The succeeding Turkish Republic has strongly opposed calling the actions a genocide.