LONDON: A photo circulating on jihadi online forums says it all: a plane flying into the Eiffel Tower with September 11 written in Arabic in red letters alongside.

The French military intervention in Mali and an Islamist militant attack on the In Amenas gas plant in Algeria in which at least 38 workers died have re-energised international jihad.

These events also closed a loop which many thought had frayed over recent years linking North African insurgents with Al-Qaeda's central leadership and ideology.

It is those links, spanning regions and times, connected through the shadowy career of Algerian militant Mokhtar Belmokhtar, which are now coming under fresh scrutiny to assess whether the west underestimated the resilience of global jihad.

Back in 1994, Algerian militants fighting the French-backed government in Algiers hijacked an Air France plane. Though it was successfully stormed by French forces in Marseille, French intelligence believed they planned to fly it into the Eiffel Tower, foreshadowing the Sept. 11 attacks on the United States.

But that Algerian phase of the jihad was overlooked by a focus on post Sept. 11 history, by hopes that Osama bin Laden's death in Pakistan in 2011 had fatally wounded Al-Qaeda, and, crucially, by a view that Belmokhtar had drifted away into making money from smuggling and seizing hostages.

"There have been a lot of debates over whether Belmokhtar is a criminal or a jihadist, but this overlooks the possibility to be both," said Stephen Tankel, a professor at American University and non-resident scholar at the Carnegie Endowment and the author of a forthcoming book on the evolution of jihadist groups since 9/11.

Algerian and western intelligence had been watching Afghan war veteran Belmokhtar for years, but they either misread his intentions or underestimated his capacity for the kind of sophisticated planning required to pull off the most dramatic terrorist act since the 2008 attack on Mumbai by the Pakistan-based Lashkar-e-Taiba militant group.

Yet the signs were there for all to read. In a post on the authoritative Jihadica website, North African specialist Andrew Lebovich noted that when Belmokhtar announced in December the creation of a new combat unit, al-Mouwakoune Bi-Dima ("Those Who Sign with Blood"), he threatened both France and Algeria.

The name he chose for his new combat unit was also the same one originally used by a group of the Algerian Armed Islamic Group (GIA) behind the hijacking of the Air France plane.

In a video in December, when he allegedly "split" from Al-Qaeda in the Islamic Maghreb (AQIM), Belmokhtar also pledged his loyalty to Afghan Taliban leader Mullah Muhammad Omar and Al-Qaeda leader Ayman al Zawahiri, without mentioning the AQIM leadership.

"He gave me the impression that he now was working independently and behaving as though he is the true emir of AQ-linked groups in the Sahel," said Camille Tawil, a journalist at al Hayat and a leading authority on north African jihadism.

True to Belmokhtar's words in that video, the hostage-takers at In Amenas made the classic demands of Al-Qaeda's central leadership - for the release from U.S. prisons of Omar Abdel-Rahman, the blind Egyptian sheikh jailed for involvement in a 1993 attack on the World Trade Center, and Pakistani neuroscientist Aafia Siddiqui, whose uncle by marriage was Sept. 11 mastermind Khaled Sheikh Mohammad.

And while it is possible the In Amenas attackers hoped to escape with foreign hostages who could be traded for money, it is equally plausible the primary motive was to re-energise global jihad at a time when French military intervention in Mali provides a powerful magnet for Islamist militants worldwide.

"In both the Air France attack and last week's assault, hostage-taking may have been an ancillary instead of a primary goal," wrote Lebovich.

"In the Air France hijacking ... it later emerged that their true goal was always to detonate the plane over Paris," he said. At In Amenas, "Algerian authorities have said the group's goal was to destroy the facility, though they may have also hoped to escape with at least some hostages."

Whatever the truth, the relationship between Belmokhtar and global jihad goes back more than 20 years. Some time after the death in Pakistan in 1989 of Palestinian scholar Abdullah Azzam, bin Laden's mentor, he left Algeria for Afghanistan.

"We were able to confirm, from a reliable source, his presence in the (training) camps which the Pakistanis were running in Peshawar," wrote the former French intelligence analyst who blogs at Le Monde newspaper under the pen-name Abou Djaffar. "There, towards the end of the 1980s, or the beginning of the 1990s, he received paramilitary training which would be very useful to him in Algeria."

By the mid-1990s he was back in Algeria, part of the Armed Islamic Group which goes by its French acronym GIA and which had sprung up to fight the government after it suppressed elections in 1992 which the Islamists were poised to win.

"The GIA quickly emerged as the most potent insurgent force in the country and the cause célèbre for many in the international jihadist movement who initially saw great promise for the Algerian jihad," said Tankel.

Bin Laden - who by then had moved from Afghanistan to Sudan - sent several emissaries to the GIA to discuss whether they wanted to join up with his then still struggling Al-Qaeda.

Lawrence Wright, author of "The Looming Tower", claimed in his book that bin Laden sent $40,000 to the GIA before regretting it as Algerian group's reputation suffered because of its appetite for mass killing during the civil war which would eventually claim up to 200,000 lives.

With the GIA discredited, infiltrated by Algerian security services and looked upon with distaste even by the global jihadi movement, the group splintered. Its most successful offshoot became the Salafist Group for Preaching and Combat (GSPC), which eventually merged into Al-Qaeda as Al-Qaeda in the Islamic Maghreb in 2007.

Over the years, the trail linking Algerian militants to core Al-Qaeda runs hot and cold, but recurs often enough to suggest a resilience in a movement which was deliberately designed with horizontal networks and an emphasis on unity of ideology which would allow it to survive the decapitation of its leadership.

According to al Hayat's Tawil, bin Laden sent an envoy, Ahmed Alwan, also known as Abu Mohamed Al-Yemeni, to the GSPC in the summer of 2001. Among the GSPC leaders he met in Algeria was Belmokhtar. "The aim of bin Laden envoy's visit was to establish links between AQ and the Algerian jihadi groups," he said.

With the GSPC running powerful networks among the North African diaspora in Europe, they may also have been linked to the assassination of Afghan Tajik anti-Taliban commander Ahmad Shah Massoud two days before the Sept. 11 attacks. His killing was seen as a present from Al-Qaeda to the Taliban then in power in Kabul, meant to undercut their opponents ahead of the expected U.S. counter-attack.

The exact links between the GSPC and Massoud's assassination by two Belgian Tunisians remain murky, though they were connected to the same network through a mosque in Paris.

In a sign of the ties that bind across regions and across years, another member of that network was Willy Brigitte, a Frenchman later convicted of planning attacks for the Lashkar-e-Taiba. His minder in Pakistan was Sajid Mir, a man who Indian authorities say was also involved in the Mumbai attacks, which killed 166 people.

"All of these guys were floating around in the same milieu at the same time," said Tankel.

The massive intelligence crackdown which followed Sept. 11 largely broke apart the European networks; but then a new link was built - between Al-Qaeda in Iraq leader Abu Musab al Zarqawi, who was killed in 2006, and GSPC leaders, which eventually convinced them to join Al-Qaeda.

The chaotic aftermath of the fall of Libya's Muammar Gaddafi in 2011 - which helped AQIM acquire weapons and exploit discontent among Tuareg tribals in the region - allowed them to expand their operations, particularly in neighbouring Mali.

But it would be a mistake to suggest they suddenly appeared out of nowhere as a new Al-Qaeda threat, given their long history with the group.

Daveed Gartenstein-Ross, author of a book on bin Laden's legacy, noted on U.S. security website Gunpowder and Lead that documents captured from bin Laden's compound in Abbottabad showed communications between AQIM and Al-Qaeda's leadership over four years, including discussion of strategic and operational issues.

"While it is possible that after bin Laden's death, when Ayman al Zawahiri became ... emir, these communications were crippled or otherwise ceased, there's no reason that this should be our a priori assumption," he wrote.

In an interview given to the Mauritanian news agency in 2011, Belmokhtar himself noted that GSPC member Younis al-Mauritani, arrested in the Pakistani city of Quetta in Sept 2011, had been sent to hold talks with Al-Qaeda leaders.

In the shadowy and often shifting alliances of global jihad, it will take time to trace all the different threads behind the attack on In Amenas.

For now though, the In Amenas raid has brought together two quite different decades - the 1990s attacks on French interests which included bombings in Paris and the Air France hijack, and the post Sept. 11 U.S.-led assault on Al-Qaeda's capabilities in Afghanistan and Pakistan.

"Maybe the leadership approved it, maybe not," Lebovich said in a phone call from Dakar. "Al-Qaeda core has been quite slow in their statements recently. It will be interesting to see if there is a statement from al Zawahiri."