Was there conflict between Anglo-Saxons and Christians in the 9th century? Certainly. Was there conflict driven by religious differences? That’s less likely, and I’ll go on to explain why.
Firstly there are some common misconceptions which should be addressed. Chief amongst these is the idea that ‘there were no pagans in Anglia/Saxony during the 9th century’, a premise that entered popular history in the Victorian era of Antiquarianism, a phase which was at best romantic and at worst revisionist. Another is the idea of Anglo-Saxons as a socially-evolved cohesive, singular group. This is also far from the truth, the only near-constant is the similarity of their language root and a belief system that shared the main pillars of Wotanism/Wodensim/Odinism.
What Was/Is Paganism?
First we need to frame ‘Paganism’, a name derived from the Latin Pagus which the occupying Romans used to describe all non-Romano-authorised religion or ritual, and that isn’t an easy task. For the purposes of answering this question it seems fair to presume that we’re talking about Paganism as the Christian churches in Anglo/Saxony and Britain saw it from the 8th century onwards, and that is to say that Paganism is any ritual, worship, deification or divine observation that wasn’t part of the Christian doctrine.
Popular Victorian histories combined with the practices of modern Druidic groups have led to a general idea that Paganism consists solely of formalised ceremonies held by white-robed, bearded Gandalf-type figures in mysterious dells. There’s no evidence to say that Druidism ever looked like that and, in any case, it was a small part of day-to-day Pagan belief by the late first millennium, if it remained a part at all. For the rest of this answer I’ll refer to Paganism as a singular despite the wide regional variations in its practice and tradition.
Were There Any Pagans Left in 9th Century Anglia/Saxonia?
Yes, lots. The claim that Christianity had enjoyed a complete conversion rate amongst Anglo-Saxons was largely based on the lack of Anglo-Saxon records from the 9th century. A primary reason for that is the largely oral culture of the Anglo-Saxons. In the 9th century writing was an occupation undertaken solely by educated clergy, lawmakers and Royal or landed sponsors who subscribed to the new resurgence of Christianity, a belief system that valued the recording in written form of imagery, histories, gospels and other works.
Anglo-Saxon life was rich with observations about the meanings of the land, sea, sky, sun, and the living things that travelled across and between them. It was rich with ritual, much of it seemingly attending to the necessities of fire, farming, life and death. So where did all that ingrained belief go after Christianity? We know there were lots of Pagans in the 8th century, and we see lots of Pagan activity and ritual in the 10th century and onwards, but did they all just hang up their hats, stop bonnin’ th’aud wych and start learning their psalms? Did they have some kind of 9th century break from the old ways?
No. There’s a mountain of evidence for the existence of Pagan ritual and the perpetuation of its calendar right inside the regular Christian liturgical procession, right up to the modern day.
Festivals and themes that were familiar to Pagans were absorbed by the Christian church and gently renamed or re-explained as part of the Christian doctrine. Non-Christians weren’t so much converted as re-trained, and the Pagan calendar was adopted quite deliberately by the new heads of the Christian Church in Anglia/Saxonia and Britain. Hutton describes this as a formalised ‘veneer’ of Christianity placed atop the ‘old ways’.
Even the date of that Christian fundamental, the Nativity, was set this way. Syrus wrote in the 4th century that ‘it was a custom of the pagans to celebrate on the same 25 December the birthday of the Sun, at which they kindled lights in token of festivity. In these solemnities and revelries the Christians also took part. Accordingly when the doctors of the Church perceived that the Christians had a leaning to this festival, they took counsel and resolved that the true Nativity should be solemnized on that day’. This re-purposing of the Pagan calendar covered the whole year, the names, symbologies and stories were new but the core beliefs remained easily intact amongst the general populace.
So Who Was Fighting?
Absolutely bloody everybody. The 9th century remained a violent time with local feuds over all the usual human minutiae like land, power, resources, pride and so on. What seems less likely is that the Anglo-Saxons were fighting each other over belief differences. We do know that the Anglo-Saxons and the Britons were doing so, or at least that the clergy of captured British lands would be instantly replaced with Anglo-Saxon clergy of the invaders.
We also know that the passage of the Great Heathen Army from its winterings in Repton and Torksey left power vacuums behind that were eagerly squabbled over but, again, religion seems incidental to this.
In all there was little need to fight to preserve the Pagan ways because the Christian church was doing a very clever job in maintaining those for everybody in everything but name. A bonus from the Christians was the assurance of everlasting life, something which seems like it may have been missing from the Pagan belief system.
Was there conflict in the 9th century between Anglo-Saxon Pagans and Christians?
Yes, lots, but Paganism and Christianity were hugely interchangeable and any fighting was not over religion.
Sources:
Understanding Medieval Liturgy: essays in interpretation; Gittos H, Hamilton S; 2019
Pagan Britain; Ronald Hutton; 1996
The Stations of the Sun: a history of the ritual year in Britain; Ronald Hutton; 2001
Physical Evidence for Ritual Acts in Pagan Britain; Ronald Hutton; 2015
The Archaeology of Churches; Rodwell W; 2012