Evidence from the liberated parts of Mosul, analysis of the Islamic State group's media output and a close examination of the recorded casualties of the operation - now approaching two months in - suggest that the city of Mosul severed as an epicentre for the Russian-speaking jihadists who make up perhaps the largest contingent of foreign fighters in Syria and Iraq.
But this is more Russiya Jadida than it is Novorossiya. Their presence in the city can be described as a brutal cocktail of the jihadi-salfism fostered in Iraq and Syria, combined with a battle-hardened sprit flowing from having seen action as far afield as Chechnya and Uzbekistan.
The involvement and importance of Russian-speaking jihadists to the Islamic State group is well documented - perhaps most notably are the likes of the now-deceased Chechen Abu Omar al-Shishani, who was able to rise to the upper-most echelons of the organisation.
The numbers are significant - as many as 3,000 Russians may have joined IS, and when other Russian-speaking nations are included, this figure is almost certainly much higher. They likely serve as the single-greatest demographic of foreign fighters in the Islamic State group outside of the Middle East and North Africa.
Hardened by brutal wars in places such as Chechnya and Dagestan, they are also some of IS' most capable military leaders and hard-line zealots.
|Iraqi special forces inspect the body of an IS fighter in Mosul.
Documents written in Russian were found upon his corpse.
Further images of corpses of Russian-speaking
fighters were deemed too explicit for publication
[Photo: Gareth Browne]
But the term "Russian-speaking" is broad - while it applies not only to Russian passport holders, but also fighters from the Caucases and even several of the central Asian republics: Kyrgyzstan, Tajikistan and even Kazakhstan.
Just this week, The Washington Post revealed the existence of the Sheikh Abu Samaya Ansari Camp in eastern Mosul. The military training centre was notably equipped with bilingual signs - both Arabic and Russian, as were gas canisters found inside the camp. Elsewhere in Mosul, as the Iraqi army advances, bilingual Qurans, written in both Russian and Arabic are being found among the possession of deceased jihadists.
On November 8, Uzbeks and Tajiks carried out suicide attacks in Mosul, and, on November 25, IS claimed a double-suicide attack in the Muharabin neighbourhood. Both bombers were from Dagestan.
The next day, the group claimed a further two suicide attacks were carried out by Chechen fighters. In fact, of the 196 Islamic State group suicide operations in Mosul tracked by analyst Charlie Winter since the start of the operation, Russian-speaking attackers have formed the largest demographic, bar Iraqis.
Joanna Paraszczuk, a researcher who specialises in tracking Chechens fighting in Syria and Iraq, has also recorded the deaths of multiple Russian-speaking fighters in Mosul in non-suicide operations.
|The Caucasians seem to have been subjected less to this and to have been allowed to remain in small, mobile units
- Kyle Orton, analyst
November 24 saw two Russian-speaking fighters - a Krgyz and Dagestani killed in fighting on the outskirts of the city. Also tracked was the death of Russian national Anatoliy Zemlianka, a "notorious" executioner killed in the outskirts of Mosul in late September.
But it is not just the foot-soldiers who appear to be Russian speakers, it's also commanders. Late September saw three Chechen IS commanders killed by coalition airstrikes on the city. The three were reportedly "responsible for administration in command of fighters in Mosul".
That fighters tend to congregate based on a shared language is far from surprising. Indeed it was noted with the Katibat al-Bataar, a formerly Libyan battalion active in Syria, which hosted an active cluster of Belgian jihadists - as noted by Pieter Van Ostayen. That so many Belgians, and indeed francophone fighters, would be associate with one another is not a coincidence, logistically it makes sense.
In combat, not being able to speak the same language as at least some of the men you were fighting with could serve as a significant barrier to military progress.
It was also the case with a group of four British fighters active in Raqqa, dubbed "The Beatles" by the British tabloid media. The group was responsible for guarding, and eventually executing, multiple western hostages. The group were all British, and though from different backgrounds, formed something of an English-speaking clique within the organisation for more than a year.
|Abu Omar al-Shishani was a notorious Chechen jihadist
Kyle Orton, an analyst with the Henry Jackson society, explains these groupings as "something that developed pretty organically".
"Different areas sent people at different times, and they often came with relatives, clansmen, and neighbours, so they stuck together."
However, this did start to cause problems and, in 2015, "[IS] started to see the cohesiveness of these units and particularly their having deeper loyalties to one-another than to the caliphate, as a problem; there were even shootouts with several foreign groups (Belgians most notably). So IS began to break the single-nationality units up, including very elite forces like Katibat al-Battar".
However, "the Caucasians seem to have been subjected less to this and to have been allowed to remain in small, mobile units that IS has deployed on its front lines from Fallujah to Mosul".
Thus it would be in keeping with the known tendencies of jihadists fighting in both Iraq and Syria that Mosul has, and remains, an epicentre for Russian-speaking Islamic State fighters.
Taleb fled the Mosul suburb of Gogjali in early September, after more than two years of IS occupation. He also made specific note of the presence of Russian-speaking fighters, telling The New Arab, "we were most afraid of the foreign fighters; the Chechens and French".
Furthermore, in a visit to Mosul's Aden neighborhood in late November, of the several dead fighters festering in the streets even several days after being killed, those from the caucuses again had a notable presence. Identifiable by their fair complexion, and ID documents found in their pockets, one Iraqi Special Forces soldier boasted that they were killing "dozens of Russians every day" - an exaggerated boast, perhaps, but certainly an indicative one.
With only 20 percent of Mosul liberated, there remains much to be learned regarding the Islamic State group's time in power in the city. But, if anything can be taken from what we have seen so far, it is that this wilayat was as much a project of Russian-speaking jihadists as it was any Syrian or Iraqi group.
Gareth Browne is reporting from the front lines of the battle for Mosul. Follow him on Twitter: @BrowneGareth