In May 2021, the Islamic State's West Africa Province (ISWAP) launched an invasion of the Sambisa Forest in Borno State, Nigeria, which served as main base of Boko Haram, a rival jihadist rebel group. Following heavy fighting, ISWAP overran the Boko Haram troops, cornering their leader Abubakar Shekau. The two sides entered negotiations about Boko Haram's surrender during which Shekau committed suicide, possibly detonating himself with a suicide vest. Shekau's death was regarded a major event by outside observers, as he had been one of the driving forces in the Islamist insurgency which has affected Nigeria and neighboring countries since 2009.