The U.S. Central Command announced the killing of ISIS leader Abu Yusif, also known as Mahmud, during a precision airstrike in the Dayr az Zawr province of Syria on December 19. The strike resulted in the deaths of two ISIS operatives and was part of ongoing efforts to prevent the reconstitution of ISIS in the region, previously controlled by the Syrian regime and Russian forces before the fall of President Bashar al-Assad.