Most of the analysis of the military defeat of Islamic State in Iraq and Syria (IS) in 2019 emphasizes that the group will continue to exist as an insurgency, conducting operations like hit-and-run attacks, planting improvised explosive devices and carrying out assassinations. While that is a legitimate point even though the extent of 'resurgence' tends to be exaggerated, a more interesting question is how differing ideological trends that have emerged from the group have reacted to this defeat.
Three trends can be identified: a 'reformist/dissident' trend that believes 'extremists' gained too much influence inside IS, 'mainstream' supporters who more or less follow IS' official media and propaganda lines and the 'extremist' trend that believes IS has deviated from its hardline positions by making concessions to the 'reformist/dissident' trend.
Of these different trends, the 'mainstream' reaction to the group's defeat is the easiest to explain. It is also the least interesting since it follows the same line as much conventional analysis: that is, stressing that IS will 'remain' (Arabic: baqiya), and that the loss of territory does not mean the true end of the caliphate. This is a line that IS' propaganda has promoted for some time.
Much more intriguing are the reactions in the 'reformist/dissident' and 'extremist' camps. As it turns out, just before the US-backed Syrian Democratic Forces (SDF) announced in March 2019 the capture of the last areas of al-Baghuz in eastern Syria from IS, a lengthy book was released online called Keep back the Hands from Allegiance to al-Baghdadi, written by former IS member Abu Muhammad al-Hashimi. He previously wrote Hashimi's Advice in summer 2017 addressed to IS leader Abu Bakr al-Baghdadi while he was still with the group in eastern Syria. Al-Hashimi's new book reflects on how IS' continual losses and internal actions have resulted in the emergence of outright opposition to al-Baghdadi within the 'reformist/dissident' trend.
The title of al-Hashimi's book is a play on the title of an earlier work called Stretch forth the hands to pledge allegiance to al-Baghdadi, written by IS cleric and scholar Turki Binali. Ironically, Binali is considered a luminary of the 'reformist/dissident' trend because he critiqued what he saw as IS' move toward 'extremism' prior to his death in a coalition air strike in 2017.
Even so, al-Hashimi emphasizes that his work is not intended to be in opposition to Binali, but rather reflects the culmination of the course Binali would have taken. He also makes clear that he does not think IS was an entirely bad experience. For example, he credits the group for having revived the understanding of the Islamic caliphate and implementing hudud punishments for serious crimes considered to be against the rights of God. He stresses that a huge coalition of countries was aligned against IS, and as such the project was not given the proper time to develop fully.
However, these caveats do not detract from al-Hashimi's main point, which is that al-Baghdadi and the IS leadership have distorted the legacy of Abu Musab al-Zarqawi and Abu Omar al-Baghdadi, the latter of whom was head of ISI [Islamic State of Iraq] in Iraq from 2007-2010, and as such was Abu Bakr al-Baghdadi's immediate predecessor. Al-Hashimi condemns Abu Bakr al-Baghdadi and the IS leadership for their oppressive and tyrannical behaviour, especially the imprisonment and killing of true scholars who tried to advise them. In so far as IS had positive aspects to it, these were the result of the work of 'honest' believers and mujahideen who, like al-Hashimi, were duped into thinking that Abu Bakr al-Baghdadi was actually the caliph. If any such people remain in IS, al-Hashimi urges them to revolt against al-Baghdadi and the group, arguing that an oppressive ruler like him has no right to be obeyed. Similarly, Khabab al-Jazrawi, a former IS member of Saudi origin who wrote the introduction to al-Hashimi's new work, urges righteous IS members in areas outside Iraq and Syria to revolt against their leaders if they are still loyal to al-Baghdadi.
From the 'extremist' end of the spectrum, the primary remaining outlet is the al-Nadhir al-Uryan channel on Telegram, a digital message broadcasting tool. The other channel, And Rouse the Believers, seems to be inactive at present. Like al-Hashimi, al-Nadhir al-Uryan has not refrained from commenting on the events that led to IS' final loss of territory in Syria. In a commentary in late December 2018, it condemned the IS leadership for persecuting the true 'monotheists' while thinking it could rely on soft-hearted individuals who would willingly denounce the group for fleeing to SDF territory.
However, the final fight in al-Baghuz resulted in an interesting shift in al-Nadhir al-Uryan's narrative. In an essay released in March 2019, it took the opportunity to lambast the 'reformist/dissident' trend, arguing that their narrative of 'extremists' wielding too much influence is ridiculous in light of the concessions that the IS leadership made to them. In reality, al-Nadhir al-Uryan argues, these 'reformists/dissidents' were planted agents, and they have proven their hypocrisy by fleeing to Idlib province in western Syria and to Turkey after previously condemning some 'extremists' for fleeing IS' persecution. In so far as 'luminaries' of the 'reformist/dissident' trend were killed, it was for acts of treason and not for their ideological views.
Meanwhile, al-Nadhir al-Uryan claims that the IS leadership abandoned its followers, leaving those adhering to the true creed and those accused of 'extremism' and betrayal to assume responsibility for defending what remained of it and its affairs in al-Baghuz. The proper course for remaining members is to realize the nature of those who abandoned them and repent the ideological deviation (jahmism, in al-Nadhir al-Uryan's words) that IS has fallen into.
On the ground, the biggest potential implication of these debates around IS' defeat is the possibility for rival successor groups to emerge. Nonetheless, it is unlikely this will actually occur for the time being. First, an important legacy of IS has been its destruction of rivals in Iraq and Syria. It is also unclear what such a rival would look like and how it would make its vision more appealing to potential recruits.
There is also the issue of how aware IS supporters around the world really are of the internal disputes that have primarily played out in Iraq and Syria and relatively small Telegram circles online. Where a split has occurred, as in West Africa, this was in a context in which there were long-standing internal problems prior to the allegiance pledge to IS. In this case, the 'extremism' and eccentricity of Abu Bakr Shekau, a charismatic figure around whom followers congregated to form the group he originally led, was at odds with IS' official West Africa affiliate. For now, little evidence has emerged of these conditions being replicated elsewhere beyond Iraq and Syria.