The islamist extremist group al-Wilāyat al-Islāmiyya Gharb Afrīqiyyah (Islamic State West Africa Province, ISWAP), formerly named Jamā'at Ahl as-Sunnah lid-Da'wah wa'l-Jihād and commonly known as Boko Haram, was formed in 2002 or 2003 in Maiduguri of Borno state in northern Nigeria.

Being inspired by the Taleban in Afghanistan and envisioning a northern Nigeria ruled under purist shari'a laws the group carried out small-scale attacks against activities they considered forbidden (haram) from their settlement near Kanamma, Yobe State.

The conflict with the Nigerian government escalated in June 2009. After riots followed by police raids on the group's compounds and reprisal attacks, clashes between police and the group's followers spread throughout northern Nigeria. Most of Boko Haram's leadership were killed and the group withdrew.

It returned in force in 2010. In June the leader of al-Qaeda in the Islamic Maghreb (AQIM) stated that his group would provide Boko Haram with weapons, training, and other support and shortly thereafter Abubakar bin Muhammad Shekau announced himself as the new leader of the group. In september 2010 Boko Haram broke into a prison in Bauchi state and freed a large number of followers and later that year set off a string of attacks on the Jos plateau. The attacks continued in 2011 with complex, large-scale attacks in Abuja, Damaturu, Madalla and Kano.

In 2012 Boko Haram was able to set up a number of bases in northern Nigeria. The unrest in Libya and Mali in 2011-2012 and the group's connections with AQIM-affiliated groups gave them access to heavy weaponry enabling them to take on the Nigerian army in open battle and expanding their territory. By the middle of 2013 they was the de facto authority in a large area along the borders of Niger, Chad, and Cameroon, creating a brutal, authoritarian state with severe punishments for those who failed to adhere to their extremist beliefs and purist rules. In August 2014 their leader Abubakar Shekau proclaimed a ”caliphate” in northern Nigeria and the group was gradually getting closer to an alliance with ISIL.

After an attack and takeover of the city of Baga by the group in january a coalition of military forces from Nigeria, Chad, Cameroon, and Niger began a campaign against Boko Haram and quickly started to regain territory from the group.

On 7 March 2015, Boko Haram's leader Abubakar Shekau pledged allegiance to ISIL via an audio message posted on the organisation's Twitter account and days later ISIL's spokesman Abu Mohammad al-Adnani welcomed the pledge of allegiance, and described it as an expansion of the group's caliphate to West Africa. Boko Haram (or Jamā'at Ahl as-Sunnah lid-Da'wah wa'l-Jihād), henceforth became the Islamic State West Africa Province, or ISWAP.

In March 2015 the coalition claimed to have retaken 11 out of 14 districts ruled by the group and in December the Nigerian president, Buhari, declared Boko Haram to have been ”technically defeated”. Despite this declaration, militants still continue to attack cities and communities in North Nigeria, and along its border with Niger, Chad and Cameroon.

Sources:
https://en.wikipedia.org/wiki/Boko_Haram
How Boko Haram Became the Islamic State's West Africa Province
By J. Peter Pham, The Journal of International Security Affairs, #30, winter 2016