SQUINT a little and the region skirting Lake Chad in central Africa resembles Mosul and Tikrit in northern Iraq: dried-out canals, scrubby plains, ragtag bands of Islamists with guns beneath an unrelenting sun. Thanks to satellite television, the long-suffering residents around the lake, which abutted Cameroon, Chad, Niger and Nigeria until it began to dry up and shrink over the past few decades (see map), have a rough understanding of what has happened recently in Iraq. They can imagine only too well being overrun by insurgents. Many see parallels between the Islamic State of Iraq and Greater Syria (ISIS), the savage group that has captured a string of Iraqi towns, and Boko Haram, the equally murderous Nigerian outfit that is striving to expand its base beyond its original area south-west of Lake Chad. The question everyone in the region is asking is whether the Nigerian bunch of beheaders can replicate the audacious territorial conquest of their Arab-led counterparts. Strolling along what used to be the shoreline before it receded, Habib Yaba, a Chadian politician from Massakory, north-east of N’Djamena, the capital, points to a white pick-up truck of unknown provenance driving across the flat lake-bed from the west. The border there is unmarked. “Look how easy it is for anyone to roam around,” he says, and goes on to describe local Islamists as increasingly numerous, well-armed and ambitious. “They rely on religious as well as ethnic links that cross the lake. And they tap into the frustrations of our people.”

Gloomy youths standing in the shade of a nearby petrol station sound ambivalent towards Boko Haram. Most would rather have jobs than become religious marauders, but given the chance they may be tempted to join a group that is evidently successful. “Not many other winners here,” says one. Their parents, sitting in cement buildings littered across a treeless expanse, say they worry that their children will be receptive to recruitment drives by Boko Haram. They also report an increase in night-time traffic, which they blame on insurgent movements.

Regional governments are fully aware of the threat and have tried to counter it. Chad is sending ever more troops to the border. Checkpoints and military vehicles are visible on the roads outside N’Djamena, which is close to the lake. A sweating colonel wearing full battledress in the midday sun swears loudly while inspecting traffic near Bongor, a town close to the border with Cameroon, 200km (125 miles) south of N’Djamena.

Oil-rich Chad has one of the fiercest armies on the continent. It has deployed peacekeepers in Mali and the Central African Republic (CAR). Earlier this year its air force took delivery of three MIG-29 jets from Ukraine, an unusually sophisticated weapon by the standards of the region. Chad also has a batch of Russian-supplied combat helicopters.

But neighbouring countries are quite a bit feebler. Nigeria’s armed forces are plagued with corruption; its rates of desertion are high. Niger is poor even by regional standards and militarily unable to cope. The weakest link in the region, however, is Cameroon.

Nigeria closed its border with it in February and has called its government negligent. Unlike Chad and Niger, it does not allow troops from neighbouring countries the right of hot pursuit across its border. That may be partly because Cameroon and Nigeria lack an agreed frontier due to a long-running territorial dispute; the UN’s attempt to mark the 2,100km boundary, which cuts across mountains and deserts, may be the biggest project of its kind in the world. In May Cameroon at last deployed a thousand troops to the border region. Within weeks they had killed 40 fighters apparently allied to Boko Haram in Kousseri, on the border with Chad. More firefights have since taken place.

In May regional heads of state met in France in an attempt to boost military and intelligence co-operation. They are backed by other Western powers. Yet old animosities, linguistic differences between Anglo- and Francophone troops, and rampant theft and incompetence mean this will have a limited effect. A glum Western diplomat says, “If the Iraqi army, aided by America and Iran, cannot stop marauding Islamists, then...”

The International Crisis Group, a Brussels-based lobby, warned in April about Boko Haram activity in “weak countries poorly equipped to combat a radical Islamist armed group tapping into real governance, corruption, impunity and underdevelopment grievances shared by most people in the region.”

In May Boko Haram fighters attacked a camp of Chinese workers near Waza, in northern Cameroon, taking ten of them hostage. This was the group’s biggest operation across the border so far. Its fighters methodically cut off the electricity supply to the camp, then besieged it for five hours before overwhelming its armed guards. Sure enough, the Cameroonian cavalry failed to turn up.

The refugee recruitment pool

The current crisis next door in the CAR has made it even harder to counter Boko Haram. More than 100,000 refugees have poured into Chad as well as into Cameroon. The border region, from Sarh to Ngaoundere, is dotted with makeshift camps. Sticks prop up ragged tarpaulins. UN officials have warned that the host countries cannot cope. The camps could become breeding grounds for further violence. “We have seen this before,” says one. “The Rwandan genocide 20 years ago begot the camps across the border in Goma and the Congolese civil war and so on.”

Arms smuggling has spiked. In the past year, government armouries in the CAR have been systematically looted, often by Islamist rebels who were beaten back with French help but managed to take the weapons with them. Local security experts report a marked increase in the sale of AK-47s as well as heavier stuff. Police have discovered several ammunition dumps apparently used by Boko Haram.

Western governments have expressed concern that Boko Haram could link up with known al-Qaeda offshoots in Libya and Somalia. But the greater immediate danger seems to be its full-scale expansion into neighbouring countries that do not yet have a strong Islamist presence.

Boko Haram’s confidence has grown since it kidnapped more than 200 Nigerian schoolgirls in April. Rather than wilting under the Western attention caused by the attack, with Michelle Obama leading the call to “bring back our girls”, the group has been boosted by the impotent reaction of regional governments. Some of the girls are thought to have been sent across Lake Chad. Many locals believe that Nigerian fighters will follow, not running away but conquering.