The Islamic State, also known as ISIS, ISIL, or Daesh, emerged as a significant militant group capitalizing on political instability in Iraq and Syria. It declared itself a caliphate in June 2014, seizing control of about one-third of Syria and 40 percent of Iraq at its peak. Its rise occurred amid the Syrian civil war and following the withdrawal of U.S. forces from Iraq, which left a power vacuum and weakened regional governance.
The group’s origins trace back to al-Qaeda in Iraq (AQI), which lost key leaders in attacks by U.S. and Iraqi forces before ISIS took over its leadership in 2010. The organization grew rapidly, benefiting from sectarian conflict, failed political institutions, and civil unrest. By 2014, ISIS controlled major cities including Mosul in Iraq and Raqqa in Syria, establishing a base for its operations and governance.
The international response to the Islamic State accelerated as its territorial expansion threatened regional and global security. In 2014, following mass executions and reports of human rights abuses, multiple countries initiated military interventions. The United States launched airstrikes in Syria and Iraq, targeting ISIS positions in an effort to degrade the group’s capabilities. Many states joined the fight against ISIS in operations coordinated alongside Iraqi and Syrian government forces, militias, and local allies.
Throughout 2015, ISIS supporters carried out several terrorist attacks outside of Iraq and Syria, demonstrating the group’s ability to inspire violence globally. Airstrikes and ground operations gradually eroded ISIS control over critical territories. By the end of 2017, ISIS had lost approximately 95 percent of the land it previously controlled.
Key battles included the retaking of Mosul in Iraq and Raqqa in Syria, which served as major turning points in undermining ISIS’s military and administrative hold. The loss of these urban centers weakened ISIS’s claim as a caliphate and diminished its operational reach. Leadership losses due to targeted attacks further disrupted the group’s command structure.
The war against ISIS spanned both the Syrian civil war and the conflict in Iraq from 2013 to 2017, involving a complex coalition of international and regional forces. The group continued to pose a threat through insurgent tactics and lone-wolf attacks despite its territorial defeat. U.S. military operations against ISIS persisted, including airstrikes into 2026, aiming to prevent the resurgence of the group in Syria and Iraq.
By early 2026, while ISIS no longer controlled large swaths of land, the organization had transformed into a decentralized insurgency. The legacy of its rise and fall marked a significant chapter in Middle Eastern conflicts and international counterterrorism efforts.
