The assassination of Boko Haram's leader on the direct orders of the new head of Isis spells trouble for northern Africa, Afghanistan - and consequently, global security at large.

Abubakar Shekau, leader of the extreme Islamist movement Boko Haram in northeastern Nigeria, died last month after detonating an explosive device while being pursued by the rival extremist faction, ISWAP (Islamic State West Africa Province). Earlier this week, ISWAP confirmed it had carried out the killing on the orders of the new head of Isis, Abu-Ibrahim al-Hashimi al-Qyurashi, who is presumed to be operating from Iraq.

It appears the motive is part of a plan to strengthen Isis influence in Boko Haram, which is itself a loose part of the wider Islamist movement that is gaining increasing influence across the Sahel region of northern Africa - and in turn, strengthening the international capacities of Isis to a worrying degree.

The killing of such an infamous Islamist leader has come at a time of increasing insecurity across the Sahel, which includes the northern part of Nigeria. And security throughout Nigeria is proving especially problematic. Nigerian President Muhammadu Buhari won an election in 2015 on a platform to increase internal security, but has concretely failed to do so.

On 30 May, 136 schoolchildren were abducted by armed gunmen - bringing the total number of student kidnappings to more than 800 in the past six months. The kidnappings are mainly down to Islamist militias in the north, but Nigeria is also facing separatist militias in the southeast and southwest.

Militias' growing influence

In spite of this, Buhari remains popular - his All Progressives Congress Party controls the parliament and most state governorships, and he is expected to be re-elected next year, so there is little prospect of changes in the security posture. This is as much bad news for Nigerian civilians as it is good news for Islamist militias, especially as their influence is growing in states to the north.

Multiple militias are involved across five countries in the Sahel - Mauritania, Burkina Faso, Mali, Niger and Chad - and many are loosely connected to al-Qaida or Isis. Isis is intent on extending its influence also throughout East and Central Africa, including the DRC and northern Mozambique. In the Sahel, the main focus is on the tri-border area of Mali, Niger and Burkina Faso, where the main Western military involvement has come from France's Operation Barkhane counter-insurgency force. The US army and the CIA are also involved, as are British special forces, and the UN maintains a substantial stabilisation mission in Mali.

However, France's role as the major operator has not been without substantial cost. As Le Monde Diplomatique put it earlier this year, the military operations, "...may be giving France an aura of European leadership in security, especially in conflicts to its south. But the costs are exploding: nearly €1bn annually; 17,000 soldiers on rotation each year (a quarter of the army's combat troops); 55 killed and 300 wounded to date; and, politically, the taint of neo-colonialism."

The conflict continues, with no end in sight, and even the deployment of a further 550 French troops earlier this year has had little effect. A sense is growing in France, as well as among its allies, that this war is unwinnable - and this sentiment is intensifying with the retreat of Western forces from Afghanistan.

In the US, the Biden administration has pushed rapidly ahead with the Afghanistan withdrawal that was ordered by his predecessor, Donald Trump. Over half of the troops have already left and most will be gone by 4 July, leaving small numbers to complete the movement of materials, and a few hundred to guard US diplomatic compounds. Most of the other NATO troops are also being withdrawn, and while this will have profound impact in and of itself, the most important element in terms of Afghan security is the substantial number of private security contractors who are leaving.

Until recently, there were 18,000 private security contractors (about half of whom were American) but most will leave within weeks. The Afghan security forces rely heavily on these contractors to repair and maintain their fleet of aircraft, armoured vehicles and a range of other equipment.

Without the contractors' help, the Afghan forces will be unable to maintain the air force longer than a few months. Analysts deem air power to be the force's main advantage over the Taliban so this loss would be a huge blow to keeping the Taliban at bay.

The US may have promised $6.6bn a year to Afghanistan over the next two years, but an indication of the scale of the problem that the Afghan forces face is that Taliban insurgents have captured nine districts since the withdrawal began a month ago, including six in the past week.

US policy after withdrawal will depend on whether the Taliban succeed in taking full control of Afghanistan and, most importantly from a Washington perspective, whether extreme groups such as Isis emerge as a direct threat to the US.

Afghan haven for Isis

The Pentagon is already planning for that possibility, particularly by maintaining the ability to deploy special forces and armed drones, but there are practical difficulties. It would suit the Pentagon if it could base forces in adjacent countries, but Iran is obviously out of the question, while attempts to sign agreements with former Soviet republics such as Kyrgyzstan, Tajikistan or Uzbekistan would meet Russian opposition, and there is no guarantee that Pakistan's leader, Imran Khan, would look kindly on a US presence.

However, the US can use aircraft carriers and amphibious warships as offshore bases. Also, the US air force has been looking into Al Dhafra air base in the United Arab Emirates as a potential option, and has recently deployed B-52 strategic bombers to al-Udeid air base in Qatar.

The Taliban, meanwhile, are making their ambitions to create a strictly Islamist country abundantly clear. A Taliban representative told Foreign Policy magazine that the group plans for Afghanistan to be a law-abiding country, a member of the community of nations, open for business, and at peace with itself, its neighbours, and the rest of the world. But the sexes will be strictly segregated, women will be forced to wear hijabs, and freedom of speech and expression will become memories.

There is little indication that the US will act to prevent this, and the wider concern is that the country becomes a haven for the likes of Isis. That risk is substantial. The attack on the Halo mine-clearance team in Afghanistan that killed ten people earlier this week and injured many more was claimed by Isis, which comes off the back of the group claiming many of the devastating bomb attacks against religious minorities in recent months.

Taliban motivations stem mainly from religious beliefs and Pashtun nationalism, with little evidence of any intention to operate against other countries.

However, that cannot be said of Isis. And if the Pentagon decides to intervene against Taliban advances in the coming months - which is especially likely if the risk arises of Kabul falling - then the Taliban could encourage the likes of Isis to retaliate overseas. This is why the Isis-ordered assassination of Nigeria's Boko Haram leader is a potent reminder of the reach and capability of this extreme movement.

From openDemocracy