FROM a ragtag band of fighters conducting sporadic raids and bombings from its hideouts, Nigeria’s Boko Haram is fast evolving into a force able to take and hold territory. In attacks on September 1st its jihadist militants overran Bama, the second-largest town in Borno state. Armed with rocket-launchers and armoured vehicles stolen from the demoralised Nigerian army, Boko Haram (its name translates loosely as “Western education is forbidden”) has moved beyond its established lairs in the Sambisa forest and the Mandara Mountains. In recent weeks it has taken several towns close to the Cameroonian border, among them Gwoza, Gamboru Ngala and Banki. (see map).

The seizure of Bama could provide a launch-pad for an attack on parts of Maiduguri, the state’s capital, about 65km (40 miles) away, with a population of more than 1m people. It was the birthplace of the insurgency. Two areas seized by the group in recent weeks form a strategic crescent around the city. Boko Haram has destroyed a series of bridges, including several close to Maiduguri, in an attempt to thwart military access and isolate parts of the state.

The grab for territory signals a change from Boko Haram’s hit-and-run tactics. This may be in keeping with pronouncements by its firebrand leader, Abubakar Shekau, that chunks of Borno state are “Muslim territory” in what appears to be an imitation of the caliphate proclaimed in parts of Iraq and Syria by Islamic State. Boko Haram has erected flags over the towns it has invaded, forcing any remaining residents to follow its strict version of sharia (Islamic law) or be killed.

Further territorial gains by the group could worsen a dire humanitarian situation. Thousands of refugees have sought sanctuary in Maiduguri, and the UN reckons that 9,000 people fleeing violence have arrived in Cameroon in the past ten days, with another 2,000 crossing into Niger, a desert nation already buckling under the pressure of taking in 50,000 refugees since May 2013.

Nigeria’s security forces have only slim prospects of rolling back the insurgency. Government soldiers are said to have fled Bama, as they did in earlier attacks on other towns; a whole battalion fled to Cameroon last month. Nigeria’s army claimed it had repelled the attack on Bama, then extended a curfew in Maiduguri. A recent report by Chatham House, a London-based think-tank, points out that soldiers in the north-east are suffering from malfunctioning equipment, low morale, desertions and mutinies. Despite a large increase in government spending on the army, little of this largesse has found its way to the front lines: many of the troops fighting against Boko Haram have been paid late, or sometimes not at all.

A change in tactics is also called for. The report argues that the army needs first of all to protect civilians. It was a little over a year ago that Nigeria’s president, Goodluck Jonathan, who is expected to run for re-election in February, made the somewhat embarrassing admission that parts of Borno state were no longer under the government’s control. Mr Jonathan’s promise to end a “serious threat to national unity and territorial integrity” looks increasingly empty. Conditions in north-eastern Nigeria are deteriorating, soldiers are breaking ranks and an emboldened terror group is gaining momentum.