The U.S.-led campaign to degrade ISIS in Iraq is experiencing early success. However, ISIS is the kind of adaptive and resilient enemy that is difficult to defeat outright. ISIS is an outgrowth of al-Qaeda in Iraq, an organization that survived the Surge and reconstituted fully despite grave military losses. ISIS has greater conventional capability than its predecessor demonstrated, but it is a hybridized force that will likely draw upon lower-profile tactics now that it is faced with a strong anti-ISIS coalition in Iraq. Hybridized warfare gives ISIS resilience and flexibility to adapt and evade defeat. ISIS’s strategy is to outlast its enemies by remaining in Iraq and Syria and expanding beyond those areas. The U.S.-led coalition will incur risk if it mistakes ISIS’s low-profile tactics as actual losses to its overall military capability.