Jama'atu Ahlis Sunna Lidda'awati wal-Jihad — popularly 'Boko Haram' (Hausa: 'Western education is forbidden') — was founded by Mohammed Yusuf at Maiduguri in 2002 in the Salafi-jihadi reaction to the post-2000 Sharia rollout in the twelve Northern states, which Yusuf judged inauthentic and entangled with the secular state. Its institutional ancestors were the Maitatsine Yan Tatsine and the Sokoto-based Izala movement.
The July 2009 'Boko Haram uprising' — five days of clashes in Maiduguri, Bauchi, Yobe and Kano that left over 800 dead — culminated in Yusuf's capture by the Nigerian Army at his father-in-law's compound on 30 July 2009 and his execution in Borno State Police custody the same evening (the killing was filmed by a bystander on a phone and broadcast on Al Jazeera). His deputies Abubakar Shekau and Mamman Nur regrouped underground. The first post-Yusuf attacks — Bauchi prison break (September 2010, 700 inmates freed) and the Madalla Christmas Day bombings (December 2011) — announced the systematic insurgency.
Between 2012 and 2015 Boko Haram took and held an area the size of Belgium in Borno, Yobe and Adamawa, declared a Caliphate at Gwoza (August 2014), abducted 276 schoolgirls at Chibok (14 April 2014), and at its peak ranked the world's deadliest terrorist organisation (Global Terrorism Index 2014–15). The Multinational Joint Task Force (Nigeria, Chad, Cameroon, Niger, Benin) under Buhari from 2015 retook most of the territory; the August 2016 Mamman Nur–Abu Musab al-Barnawi split produced ISWAP (Islamic State West Africa Province), which by 2020 had eclipsed the Shekau faction. Shekau was killed on 19 May 2021 at Sambisa Forest in fighting with ISWAP.
Conservative death toll across the insurgency: 35,000–40,000 killed in direct violence, 350,000+ deaths overall when starvation, disease and displacement are included (UNDP 2021). Two million IDPs at peak; about 110 of the Chibok girls remain unaccounted for. The underlying conditions in the Borno-Yobe-Adamawa triangle — 90% multidimensional poverty, 80% illiteracy, climate-driven Lake Chad collapse (90% surface-area reduction since 1960), no state presence in much of the rural sector — remain untouched. The exact formula — state kills the political leader of a millenarian Northern movement, the armed successor radicalises and survives — was first established in 1980 with Maitatsine.