ISIS has lost 98% of the territory it once had in Syria, but that doesn't necessarily mean the US has defeated it - Business Insider:

President Trump has announced that the US has defeated ISIS in Syria and that he plans to pull back all 2,000 US troops from the country. Since then, there have been contradictory statements from administration officials at the highest level. ....
https://www.pri.org/stories/2019-01-14/when-us-pulls-out-syria-what-happens-isis