In May 2021, the Islamic State's West Africa Province (ISWAP) launched an invasion of the Sambisa Forest in Borno State, Nigeria, which was serving as the 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 as a major event by outside observers, as he had been one of the main driving forces in the Islamist insurgency in Nigeria and neighboring countries since 2009.

Background

Salafi jihadist Boko Haram is centred in Borno State in northeastern Nigeria. It launched an insurgency against the Nigerian government following an unsuccessful uprising in 2009. Supported by several other jihadist groups including al-Qaeda, the group aimed at establishing an Islamic state in northern Nigeria. From 2012, the Sambisa Forest became the center of Boko Haram's self-proclaimed territory. Boko Haram extended its actions into Cameroon, Chad and Niger during the mid 2010s, greatly increasing its power and territorial holdings in the Chad Basin in 2014. Its de facto leader Abubakar Shekau consequently attempted to increase his international standing among Islamists by allying with the prominent Islamic State (IS). Boko Haram thus became the "Islamic State's West Africa Province" (ISWAP).

When the insurgents were subsequently defeated and lost almost all of their lands during the 2015 West African offensive by the Multinational Joint Task Force (MJTF), discontent grew among the rebels. Despite orders by the IS central command to stop using women and children suicide bombers as well as refrain from mass murdering civilians, Shekau refused to change his tactics. Researcher Aymenn Jawad Al-Tamimi summarized that the Boko Haram leader proved to be "too extreme even by the Islamic State's standards". Shekau had always refused to fully submit to the IS central command, and the latter consequently removed him as leader of ISWAP in August 2016. Shekau responded by breaking with the IS central command, but many of the rebels actually stayed loyal to IS. As result, the rebel movement split into a Shekau-loyal faction ("Jama'at Ahl al-sunna li-l-Da'wa wa-l-Jihad", generally known as "Boko Haram"), and a pro-IS faction led by Abu Musab al-Barnawi (which continued to call itself "Islamic State's West Africa Province"). These two groups have since clashed with each other, though they possibly occasionally cooperated against the local governments. In addition, Shekau never officially renounce his pledge of allegiance to IS as a whole; his forces are thus occasionally regarded as "second branch of ISWAP". Overall, the relation of Shekau with IS remained confused and ambiguous.

In the next years, Barnawi's ISWAP and Shekau's Boko Haram both reconsolidated, though ISWAP grew into the more powerful group. Whereas Shekau had about 1,000 to 2,000 fighters under his command by 2019, the Islamic State loyalists counted up to 5,000 troops. Furthermore, ISWAP displayed signs of increasing sophistication and growing connections to the IS core group. Barnawi's followers did not just align ideologically with IS, but also adopted its technologies and tactics. They began using suicide vehicle-borne improvised explosive devices and drones which experts considered evidence of support and advice by exiled IS members from Syria and Iraq.

ISWAP also focused on military targets and attempted to win the support of the local civilians, unlike Shekau whose forces were notorious for massacring and kidnapping non-combatants. The Islamic State employed a "hearts and minds" policy toward the local communities, gradually winning substantial grassroots support, and implemented its own government, including collecting taxes. Despite not fully controlling the areas where it is present, ISWAP maintains more control over large swaths of the countryside than the Nigerian government and has created four governorates. It offers some "limited services", and encourages locals to live in de facto rebel-held communities. At the same time, it has targeted agencies providing humanitarian aid, thereby depriving locals of basic necessities in government-held areas. However, Shekau's group would often raid communities under ISWAP protection, and punish civilians who had cooperated with the Islamic State. This further motivated ISWAP to eventually deal with Boko Haram one way or another. Al-Naba, the Islamic State's official newspaper, later claimed that Shekau's activities had disrupted local communities to such a degree that famine had become a major issue, allegedly making an intervention of ISWAP necessary.

ISWAP followed a reconciliatory approach in regards to Shekau's followers. Whereas Boko Haram usually executed captured ISWAP fighters as traitors, ISWAP would only disarm and preach to captured Boko Haram troops before releasing them. This resulted in many of Shekau's fighters developing sympathies for the Islamic State faction. ISWAP repeatedly stated that it was only opposed to Shekau, arguing that they had no issues with other Boko Haram members. In addition, the Islamic State faction deviated from Shekau's brutal and autocratic leadership style by organizing a powerful shura or committee that gave the group an element of "democracy". As a result, ISWAP gained more popular support, yet also became more prone to leadership struggles. In the course of the Chad Basin campaign (2018–2020), a violent dispute among ISWAP resulted in the deposition of Abu Musab al-Barnawi and the execution of several commanders.

Prelude By 2021, ISWAP had surpassed Shekau's group in numbers, weaponry, and "ability". It began to expand its holdings across northern Nigeria and Cameroon. As the Islamic State forces clashed with Boko Haram, the former generally emerged better off. Meanwhile, Shekau's group was weakened in clashes with the Nigerian Armed Forces and the military of Chad. Several Boko Haram commanders defected to ISWAP, some of which began to operate as spies within Shekau's force.

In February 2021, ISWAP and Boko Haram engaged in a battle at the Niger–Nigeria border after the former had abducted women who were linked to the latter. Around this time, a faction of ISWAP also defected to al-Qaeda. The violence between ISWAP and Boko Haram further escalated after the former had tried to convince the latter to change its tendency to overuse takfir (non-believer) designations. The Nigerian newspaper Vanguard stated that ISWAP had previously sent especially loyal troops for training to Libya, Somalia, and Syria; these forces returned to Nigeria in March and April, greatly bolstering the local Islamic State forces and allowing them to operate more aggressively against Boko Haram.

In April 2021, Boko Haram ambushed an ISWAP brigade, killing several militants. Around this time, dissatisfaction within Boko Haram reportedly rose due to Shekau executing his chief of staff Abu Fatima. The inter-rebel fighting was paused during Ramadan. Around mid-May, ISWAP released an audio declaring that Abu Musab al-Barnawi had been reinstated by the IS central command as "caretaker" leader of ISWAP. As al-Barnawi had been the one to depose Shekau in the first place, analyst Jacob Zenn argued that this move was a sign that both the IS central command and ISWAP wanted to finally eliminate Shekau. At the same time, the shura and sectional leaderships of ISWAP were temporarily dissolved. Vanguard claimed that delegates of the IS central command had visited ISWAP shortly before the offensive against Sambisa Forest. Al-Naba also vaguely stated in an article that ISWAP had been ordered to eliminate Shekau, hinting that the IS central leadership had been involved in the decision making process. Conspiracy theories circulated which alleged that non-Jihadist outside powers had been involved in the escalation of the inter-rebel conflict, arguing that it was part of a wider rivalry between "Anglophone Nigeria and its Francophone neighbors".

The Islamic State forces moved their civilian followers to more secure locations around Kukawa in preparation of the anti-Shekau operation.

Battle Early ISWAP offensive

ISWAP began its offensive on 14 May, targeting four minor camps as well as Shekau's main base located in the Sambisa Forest. While al-Barnawi acted as ISWAP chief commander, Muhammad Dawud (alias "Abu Hafsat") coordinated the offensive alongside Islamic State officers of the Lake Chad area, Timbuktu triangle and Marte. One of the most important frontline officers involved in the operation was Bako Gorgore, ISWAP's Timbuktu governor and commander. ISWAP would use "mobile columns" to great effect during the battle, gradually cornering Shekau's loyalists. The ISWAP columns reportedly contained many fighters who were very familiar with the Sambisa Forest and Shekau's "routine".

According to al-Naba, the ISWAP troops launched a nightly attack from late 14 May, intending to surprise the Boko Haram defenders. Even though the ISWAP troops had to cross mine fields, the plan succeeded, and they were able to strike at Shekau's main base early during the next day. Boko Haram responded with mortar fire and used several suicide bombers, one of them in a car, to halt ISWAP's advance. However, the ISWAP militants reportedly managed to kill most suicide bombers before they reached them, with only three succeeding in detonating themselves, inflicting only minor damage. After ISWAP had inflicted heavy losses on Boko Haram including two vehicles destroyed, the base's defenders fled. However, ISWAP failed to capture Shekau during this clash as it had initially intended to do. The Islamic State troops spent the remaining day securing the captured Boko Haram base. According to al-Jazeera, both sides lost several fighters during the confrontation.

On 16 May, ISWAP began to eliminate the remaining Boko Haram resistance. Using motorcycles and dozens of technicals outfitted with heavy weapons, ISWAP chased the Boko Haram troops outside the bases, killing many and convincing more to surrender. Several Boko Haram "top fighters" outright defected. According to an alleged insider account, up to 70% of Boko Haram's qaids (senior commanders) had secretly sided with ISWAP by the time of the operation. One group of Boko Haram loyalists, counting "dozens" according to al-Naba, holed up at the well defendable Ghowbra camp. ISWAP attacked the camp but broke off the assault after an hour of fighting. ISWAP spent the next day securing the captured areas, continuing to search for Shekau, and patrolling through the forest with voice amplifiers announcing its aims and requesting Boko Haram stragglers to surrender. On 18 May, Shekau gave a final sermon. His tone indicated he knew that he "was near the end". The sermon suggested that many Boko Haram fighters had been killed, but Shekau also reaffirmed that he "would never be loyal to anybody". He also reaffirmed his ideological stances. However, the Boko Haram leader claimed that he had never rebelled against Abu Ibrahim al-Hashimi al-Qurashi, the Islamic State's caliph, blaming his local rivals for the rebel infighting.

Shekau's death and end of the ISWAP operation