The authors claim that the Islamic State moved its forces undercover during the multinational military campaign that eventually sacked its self-proclaimed caliphate. They go on to explain that by “deliberately withdrawing and relocating may of its fighters and their families”, the group managed to preserve a large part of its fighting forces, which are “now dispersed across [Iraq and Syria] and are waging a capable insurgency”. The latter is funded through ISIS’ global finance network and armed with weapons and other war materiel that the group managed to hide in tunnel systems and other hidden facilities. Islamic State insurgents have thus been engaged in a broad and largely successful campaign to assassinate village and town elders across Iraq, and have even reestablished a sharia-based taxation system in some of Iraq’s predominantly Sunni areas. The group also retains a significant presence in Syria, where it continues to battle the Syrian regime, US-supported Kurdish forces, and other Sunni militant groups, including al-Qaeda, according to the report.

The report’s authors place much of the blame for ISIS’ resurgence at Washington’s door, describing America’s hasty military withdrawal from Iraq and Syria as “a critical mistake”. In its recommendations section, the report calls on the United States to develop and implement a long-term counter-terrorism strategy against ISIS, which will combine military and community-building measures. “Another limited [military] intervention will not be sufficient” to eliminate the threat, the report’s authors claim.