The U.S. says it is withdrawing a dozen warplanes from a Turkish air base, barely a month after they arrived to help Turkey protect its air space and to conduct airstrikes against Islamic State targets in Syria and Iraq.

The decision was announced Wednesday by U.S. European Command, one day after Defense Secretary Ash Carter visited Incirlik Air Base, where the six F-15 Eagles and six F-15 Strike Eagles arrived last month. A Pentagon spokesman, Navy Capt. Jeff Davis, said the timing was a coincidence.

The U.S. still has 12 A-10 close-air support aircraft based at Incirlik, as well as drone aircraft.

During his visit to Incirlik, Carter said he is looking for ways to do more to hasten the defeat of the Islamic State group.