The Syrian Democratic Forces (SDF) announced in March that ISIS had lost its final stronghold in Syria, marking the end of the so-called caliphate it declared in 2014. Six months later, President Trump announced the death of Abu Bakr al-Baghdadi in a night-time raid by U.S. special forces on his compound in Syria. Clearly 2019 was a year of significant strides in the war against ISIS. So why are so many in the international community now worried that the terrorist group is in resurgence?