Africa has become the “epicenter of global terrorism,” and it will take “sustained pressure” to address the threats, U.S. Africa Command leader Gen. Dagvin Anderson told lawmakers on Tuesday.

Anderson’s testimony in front of the House Armed Services Committee coincided with a series of recent joint U.S.-Nigerian operations targeting Islamic State fighters. The Nigerian military said on Tuesday that the joint strikes had killed 175 ISIS members, including Abu Bilal al Minuki, whom Anderson called “the most active and impactful terrorist in the world.”