Attacks by non-state armed groups are a security challenge in the Sahel, including Nigeria. In northern Nigeria, the activities of Jama'at Ahl al-Sunna li al-Da'wa wa al-Jihad (also known as Boko Haram), Islamic State West Africa Province (ISWAP) and Jama’atu Ansarul Muslimina fi Biladis Sudan (Ansaru) contribute to the instability of the Nigerian state.On 16 August 2025, Nuhu Ribadu, Nigeria’s national security adviser, announced the arrest of two leaders of Ansaru: Mahmud Muhammad Usman and Mahmud al-Nigeri. They appeared before the Federal High Court in Abuja on 11 September. Usman pleaded guilty to the charge of illegal mining activities and was sentenced to 15 years’ imprisonment. They are currently facing a 32-count charge including engagement in acts of terrorism, and other violent crimes. As a scholar of security studies, I can offer some thoughts about the importance of the arrest, possible responses from Ansaru and how Nigeria should respond. Who are the two men arrested?Mahmud Muhammed Usman and Mahmud al-Nigeri are two key leaders of Ansaru, a terrorist organisation that formed as a breakaway faction of Boko Haram in 2012 in Kano state. Boko Haram is a Salafi Jihadist militant group operating in north-east Nigeria and the Lake Chad region. It’s known for its efforts since 2010 to establish an Islamic state governed by Islamic law.Ansaru functioned until 2013 before it appeared to fizzle out. Its operations included a prison break in November 2012, an attack on a Nigerian military convoy heading to Mali in January 2013 and the kidnapping of seven expatriates working with Setraco Construction Company in Bauchi in February 2013. Since 2013, not much has been heard about the group. Some linked its silence to the death of its leader Abubakar Adam Kambar in 2012. Others said it had been forced back into mainstream Boko Haram by that group’s then leader Abubakar Shekau.But Ansaru revived between 2018 and 2020 and has been recruiting and involved in rising banditry and kidnapping in North West and North Central. The arrested leaders are prominent figures in Ansaru. An official statement revealed that Mahmud Muhammad Usman is the amir (leader) and Mahmud al-Nigeri serves as the deputy and chief of staff. Both have undergone extensive training from al-Qaeda in the Maghreb region. Al-Qaeda is a pan-Islamic militant group leading a global Islamist revolution aimed at uniting the Muslim world. It was established by Osama Bin Laden in 1988 and he remained its leader until 2011, when he was killed.Strategic significance of the arrestArresting leaders is known in counterterrorism as “leadership decapitation” or “snakehead strategy”. This involves capturing or killing the leaders or high-ranking commanders of terrorist organisations. Not all policymakers and academics agree about the effectiveness of that tactic. States facing terrorism challenges, such as Israel, the United States and Russia, often use it, but most research shows it is not that effective. It may temporarily incapacitate the group, but the group may bounce back even more brutally.The targeted killing of Osama Bin Laden decimated al-Qaeda but paved the way for the rise of the Islamic State as a global caliphate. Islamic State has been lethal in its operations, particularly in the Sahel. And the 2009 killing of Muhammed Yusuf, the former leader of Boko Haram, led to the emergence of Abubakar Shekau. Under him, Boko Haram became more formidable until he died in 2021.The case of the Ansaru leaders is different, however. It is target arrest and incarceration. This strategy has advantages for Nigeria and the broader Sahel region.Incarceration of the two leaders means Ansaru won’t be able to take key decisions for some time. And it will deny the group some key technical know-how. Terrorist organisations seldom get new leaders while others are still alive.Al-Nigeri is not only deputy and chief of staff, he is an expert in planning and implementing attacks and kidnapping in Nigeria and Niger. He underwent training in the Maghreb in handling weapons and making explosive devices. It’s possible that lack of access to their expertise and authority will drastically reduce the activities of Ansaru.Shortly after their arrest, Abduraham Yusuf, son of the Boko Haram founder, who is also a leader of one of ISWAP cells in the region, was arrested in Chad. Similarly, Boko Haram leader Ibrahim Mahamadu, also known as Bakura, was reportedly killed in Niger Republic on 20 August. I believe these two incidents may be related to intelligence obtained following the arrest of the two Ansaru leaders. Likely responses from the groupConsidering the importance of the two leaders to Ansaru, there are two likely responses from the group. breaking them out of prison – the group carried out prison breaks in 2012 and 2022 high-profile kidnapping and hostage taking, a trademark of Ansaru.The March 28 2022 Abuja-Kaduna train bombing incident was believed to have been carried out by Ansaru with the support of some bandits as a retaliation for the Nigerian Police raid of Ansaru Camp in Kaduna State in which two commanders of the group were killed. Even the parent group, Boko Haram, possibly executed the Chibok kidnapping in 2014 in retaliation for some of its commanders under incarceration of Nigerian government. Given these antecedents, the arrest of their prize leaders may trigger retaliation from the group. Although the group’s ability to retaliate largely depends on whether it can still function effectively without the inputs of its two leaders in incarceration, the current cordial relationship between Ansaru and some bandits operating in the North West may make this possible. Responses from the stateThe Nigerian government and security forces must brace for likely retaliation from Ansaru. I expect that these two leaders should not be kept together in the same prison facility, and there is a need to adequately fortify prison facilities where they are kept to fend off any possible attack. Furthermore, security needs to be provided for key places, especially schools, communities, and other vulnerable people that Ansaru may attack in the North West and North Central regions.Saheed Babajide Owonikoko does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.