Lagos - Long before Boko Haram's uprising plunged the region into crisis, the area below Lake Chad was part of a powerful Islamic empire, known for religious piety and unity spanning roughly 1 000 years.
The scope of the Kanem-Bornu empire changed repeatedly from its founding in the ninth century to its downfall in the 1890s but at its height the kingdom included modern day northeast Nigeria, as well as parts of neighbouring Cameroon, Chad and Niger.
Boko Haram, which has claimed to be fighting to create an Islamic state in Nigeria, has widened its insurgency through attacks in Cameroon and, more recently, Chad and Niger, where the group launched its first-ever strikes this month.
Those hardest hit by the violence are ethnic Kanuris, a community represented in all four nations and which also led the Kanem-Bornu empire.
Also Read:Boko Haram violence hits fish industry in NE Nigeria
Experts say that Boko Haram has at times tried to invoke the Kanem-Bornu legacy, recalling a pious pre-colonial empire that transcended European-imposed borders to justify attacks against targets it deems un-Islamic.
But that strategy is almost certain to fail as the insurgents' relentless massacres and kidnappings have destroyed any credibility they may have had among the Kanuri, analysts said.
Citing the fallen empire to legitimise a modern jihad "will not catch on at all", said Professor Sidiqque Mohammed, of Nigeria's Ahmadu Bello University.
Boko Haram's leaders "have no sense of history", he told AFP.
A 'great empire'
Kanem-Bornu was a centre of Islamic scholarship, attracting visitors from across the Sahel and Arab areas further east, according to Vincent Hiribarren, a professor at King's College, London, and author of the forthcoming book, "A History of Borno".
The empire's remarkable cohesion over a millennium was partly forged through a commitment to Islam, he said.
"It is something (the Kauri) are very proud of", he said, adding that people in the region often speak of "the great empire".
A source of particular pride was the empire's continued independence in the face of advances by a neighbouring caliphate founded by Usman Dan Fodio, a revered 19th-century jihadist.
In carving out what was one of the largest states in West Africa, Dan Fodio conquered most of modern-day northern Nigeria and chunks of neighbouring states. His caliphate based in the city of Sokoto fell to British colonialists in 1903.
But Sokoto's attempt to topple Kanem-Bornu was eventually repelled by the empire's mostly Kanuri forces.
Some experts say this bitter history still strains relations between the Kanuri and the Hausa and Fulani ethnic groups that dominate the rest of northern Nigeria.
But it also complicates efforts to understand the recent rhetoric used by Boko Haram.
A video message from Boko Haram leader Abubakar Shekau, believed to be Kanuri, released on February 17 included a celebratory reference to Dan Fodio.
Hiribarren and other academics said there is evidence of Shekau and the group's late founder Mohammed Yusuf citing Kanem-Bornu as part of their ideological rejection of the Nigerian state.
The precise record is unclear with respect to public messages, including Yusuf's sermons which were widely distributed before his 2009 death and videos released by Shekau.
But most agree that some Boko Haram commanders have invoked the great Kanuri Islamic legacy in trying to attract or indoctrinate new fighters.
"It is a reappropriation of a glorious past," said Hiribarren.
Yan St-Pierre, who heads the Modern Security Consulting Group, agreed that Boko Haram has used Kanem-Bornu to create "historical legitimacy".
Also Read: Army unearthes terrorists posing as women in Baga
But, he noted, the insurgency has demonstrated an "ideological devolution" since its founding in 2002 and this use of history probably has limited impact now.
The Islamist movement which began under Yusuf, partly drawing members from those frustrated with Nigeria's woeful governance, has over the last five years morphed into a ruthless rebellion that deliberately targets defenceless civilians, including children.
Any claim by Shekau or his deputies to be fighting for the reclamation of Kanem-Bornu is also undermined by Boko Haram's multiple assassination attempts against the empire's living heir, Umar Garbai El-Kanemi, known as the Shehu of Borno, who is Nigeria's number three Islamic cleric.
Cross-border attacks have little to do with empire restoration and more to do with revenge against the militaries of Cameroon, Chad and Niger who are now cooperating with Nigeria to crush the insurgency, St-Pierre said.
For Hiribarren, the spreading conflict means the Nigerian militants are being exposed to a wider network of Kanuri people who share "a cultural community of people who speak the same language and who used to be part of the same kingdom.
"Is Boko Haram capitalising on this? I'm not so sure," he said.