Boko Haram, which calls itself Wilāyat Gharb Ifrīqīyyah (Arabic: الولاية الإسلامية غرب أفريقيا, (Islamic State's) West Africa Province, ISWAP), and was formerly called Jamā'at Ahl as-Sunnah lid-Da'wah wa'l-Jihād' (Arabic: جماعة أهل السنة للدعوة والجهاد, "Group of the People of Sunnah for Preaching and Jihad"), is an Islamic extremist group based in northeastern Nigeria, also active in Chad, Niger and northern Cameroon. The group is led by Abubakar Shekau. Estimates of the group's membership varies between 7,000 and 10,000 fighters. The group initially had links to al-Qaeda, but in 2014, it expressed support for the Islamic State of Iraq and the Levant before pledging formal allegiance to it in March 2015.
After its founding in 2002, Boko Haram's increasing radicalization led to a violent uprising in July 2009 in which its leader was summarily executed. Its unexpected resurgence, following a mass prison break in September 2010, was accompanied by increasingly sophisticated attacks, initially against soft targets, and progressing in 2011 to include suicide bombings of police buildings and the United Nations office in Abuja. The government's establishment of a state of emergency at the beginning of 2012, extended in the following year to cover the entire northeast of Nigeria, led to an increase in both security force abuses and militant attacks. Boko Haram has killed more than 17,000 people since 2009, including over 10,000 in 2014, in attacks occurring mainly in northeast Nigeria.
650,000 people had fled the conflict zone by August 2014, an increase of 200,000 since May; by the end of the year 1.5 million had fled. Corruption in the security services and human rights abuses committed by them have hampered efforts to counter the unrest. Since 2009, Boko Haram have abducted more than 500 men, women and children, including the kidnapping of 276 schoolgirls from Chibok in April 2014.
In mid-2014, the militants gained control of swathes of territory in and around their home state of Borno, estimated at 50,000 square kilometres (20,000 sq mi) in January 2015, but did not capture the state capital, Maiduguri, where the group was originally based. A military coalition including Chad and Niger have since displaced the group from most of its occupied territories, although it still controls southern parts of Borno State.