That would be the Middle East itself: https://en.wikipedia.org/wiki/Islamic_State

To fight ISIS, it is mostly a joint effort of US + NATO + Allies: https://en.wikipedia.org/wiki/Combined_Joint_Task_Force_%E2%....

> The United States accounts for the vast majority of airstrikes (75–80%), with the remainder conducted by Australia, Canada, Denmark, France, Jordan, Belgium, the Netherlands, Saudi Arabia, Turkey, the United Arab Emirates, and the United Kingdom.