The reappearance of the Isis leader Abu Bakr al-Baghdadi has the same shock effect as that of Osama bin Laden in the aftermath of 9/11. It has all the greater impact because of claims that, with the elimination of the last territory held by Isis in March this year, that group was close to being out of business as a serious threat.

The slaughter of some 250 civilians in Sri Lanka had already showed that Isis retains its ability to take control of the international news agenda with suicide bombing attacks directed at civilians. “As for our brothers in Sri Lanka, I was overjoyed when I heard about the suicide attack, which overthrew the cradles of the Crusaders, and avenged them for our brethren in Baghouz,” al-Baghdadi said.

Just before the bombings in and around Colombo, the leader of the Isis cell had pledged allegiance to al-Baghdadi.

How much is really changed by the first video in five years of the Isis leader? His re-emergence certainly has a symbolic significance, because he had been reported dead or gravely wounded so many times. It adds to the sense that, even after Isis has suffered a series of defeats, it still exists as a working organisation, even if its military strength is much depleted.

But the last time that al-Baghdadi appeared in 2014 it was in the Grand Mosque in Mosul, the city which Isis had astonished the world by capturing with limited forces fighting a large and well-equipped Iraqi army. Isis presented its victory – and many more that followed – as a sign of divine favour.

Timeline of the Isis caliphate Show all 19 1 /19 Timeline of the Isis caliphate Timeline of the Isis caliphate ISIS began as a group by the merging of extremist organisations ISI and al-Nusra in 2013. Following clashes, Syrian rebels captured the ISIS headquarters in Aleppo in January 2014 (pictured) AFP/Getty Timeline of the Isis caliphate Abu Bakr Al-Baghdadi declared the creation of a caliphate in Mosul on 27 June 2014 Timeline of the Isis caliphate Isis conquered the Kurdish towns of Sinjar and Zumar in August 2014, forcing thousands of civilians to flee their homes. Pictured are a group of Yazidi Kurds who have fled Rex Timeline of the Isis caliphate On September 2 2014 Isis released a video depicting the beheading of US journalist Steven Sotloff. On September 13 they released another video showing the execution of British aid worker David Haines Timeline of the Isis caliphate The US launched its first airstrikes against Isis in Syria on 23 September 2014. Here Lt Gen William C Mayville Jnr speaks about the bombing campaign in the wake of the first strikes Getty Timeline of the Isis caliphate Isis militants sit atop a hill planted with their flag in the Syrian town of Kobani on 6 October 2014. They had been advancing on Kobani since mid-September and by now was in control of the city’s entrance and exit points AFP/Getty Timeline of the Isis caliphate Residents of the border village of Alizar keep guard day and night as they wait in fear of mortar fire from Isis who have occupied the nearby city of Kobani Getty Timeline of the Isis caliphate Smoke rises following a US airstrike on Kobani, 28 October 2014 AFP/Getty Timeline of the Isis caliphate YPG fighters raise a flag as they reclaim Kobani on 26 January 2015 VOA Timeline of the Isis caliphate Isis seized the ancient Syrian city of Palmyra on 20 May 2015. This image show the city from above days after its capture by Isis Getty Timeline of the Isis caliphate Kurdish forces are stationed on a hill above the town of Sinjar as smoke rises following US airstrikes on 12 November 2015 AFP/Getty Timeline of the Isis caliphate Kurdish forces enter Sinjar after seizing it from Isis control on 13 November 2015 AFP/Getty Timeline of the Isis caliphate Iraqi government forces make the victory sign as they retake the city of Fallujah from ISIS on 26 June 2016 Getty Timeline of the Isis caliphate Iraqi forces battle with Isis for the city of Mosul on 30 June 2017 AFP/Getty Timeline of the Isis caliphate Members of the Iraqi federal police raise flags in Mosul on 8 July 2017. On the following day, Iraqi prime minister Haider Al Abadi declares victory over Isis in Mosul Getty Timeline of the Isis caliphate Members of Syrian Democratic Forces celebrate in Al-Naim square after taking back the city of Raqqa from Isis. US-backed Syrian forces declare victory over Isis in Raqqa on 20 October 2017 after a four-month long campaign Getty Timeline of the Isis caliphate Female fighters of the Syrian Democratic Forces celebrate in Al-Naim Square after taking back the city of Raqqa from Isis. US-backed Syrian forces declare victory over Isis in Raqqa on 20 October 2017 after a four-month long campaign AFP/Getty Timeline of the Isis caliphate Trucks full of women and children arrive from the last Isis-held areas in Deir ez-Zor, Syria in January 2019 They were among the last civilians to be living in the ISIS caliphate, by this time reduced to just two small villages in Syria’s Deir ez-Zor Richard Hall/The Independent Timeline of the Isis caliphate Zikia Ibrahim, 28, with her two-year-old son and 8-month-old daughter, after fleeing the Isis caliphate, on Saturday 26 January 2019 Richard Hall/The Independent

But it was Isis fighters who blew up what remained of the Grand Mosque when they were losing the nine-month long siege of Mosul in 2017. The reappearance of al-Baghdadi comes at a moment of defeat rather than victory.

Isis has made immense efforts to keep al-Baghdadi alive when so many of its other leaders are dead. He may have been secretly living inside Mosul until about halfway through the siege. Iraqi army commanders believed at the time that a sudden sortie by Isis, deploying large numbers of suicide bombers, which temporarily breached the siege lines, was a successful bid to get al-Baghdadi to safety before it was too late.

Isis fighters were uncertain last year if he was alive or dead according to local people in eastern Syria. They reported that the fighters had been told by their emirs (commanders) that the long-term fate of their movement did not depend entirely on his survival. Many wondered if he was already dead.

His reappearance raises another question: how far and in what ways had Isis prepared for the end of its territorial caliphate that in 2014-15 stretched from the outskirts of Baghdad almost to the Mediterranean? For all their fanaticism, Isis military commanders are skilled and experienced men who knew that they were bound to lose a positional war with their many enemies.

They prepared hideouts, supplies, weapons and a cadre of experienced fighters and organisers to ensure that their movement would live on after the loss of the town of Baghouz in eastern Syria, where they made a last stand.

There are plenty of places in which to hide in the vast deserts of western Iraq and eastern Syria where there are increasing numbers of bombings and assassinations in territories where Isis once ruled, including in Raqqa and Mosul, its de facto capitals in Syria and Iraq.