How do you think that'd affect the greater scope of things from what I've read Charlemagne essentially led the charge In converting Pagan Europe to catholicism. Would a Saxon victory change the course of the middle ages?
The absence of Charlemagne certainly changes things. Chances are, this scenario prevents his coronation by the Pope. If the Frankish realm splis apart after Charlemagne's death (which is not unlikely at all), the Western Imperial idea has just been aborted. That dramatically changes the course of Western culture.
It's also good news for the Slavs and Balts, who will likely be pushed East far less comprehensively by the Germans.
Paganism gets a reprieve, but as has been noted: probably a temporary one. I'd argue that defeating Charlemagne is going to be
the defining "national" moment, so eager conversion to Christianity in the short(er) term is unlikely. You'd see the Saxon realm closely tied to Scandinavia, which would also be Pagan at this time. They'd be foreign and hostile to the Christian realms, so in this ATL, I could see the whole Viking period being much more of "Pagan scourge upon the Christians" kind of thing.
Some alt-Knut figure might even be able to unite all the Germanic Pagans realms under his sole rule, which would be a great boon.
But would it be enough? I don't think so. The way to avoid gradual conversion is dedicated hostility to the spread of Christianity (e.g. always kill missionaries and send their heads back as a warning). This automatically creates the side-effect that the Christians
hate you, and will want to stamp out your "heathen cult".
It's highly probable that the Slavs will be converted as in OTL. They'll probably all go Orthodox, though. The Balts, too -- it'll be Orthodox Slavic Christians from the South and East fighting them, instead of also having Catholic German Christians coming from the West. But the ultimate outcome is the same. (In AH circles, the idea is occasionally raised of some pan-pagan alliance against the Christians, i.e. Saxons teaming up with Balts and Fins, but that's a silly pipe-dream. The idea of "paganism" as a shared identity is a thoroughly
modern concept.)
So the result is: a Pagan "wedge" covering a large part of the Scandinavian peninsula, and Denmark, and the greater Saxon region. This is vulnerable to attacks from all sides. And as noted: it would attract such attacks. I expect "Crusades" to be far more of a Northern affair than in OTL.
Even if the Catholic West is irrepairably weakened and far more fractured into smaller states than in OTL (with the Franish realm being split permanently, and Germany never forming)... they're not likely to be weak
forever.
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Redbad killing Charles Martel, and the Frankish realm collapsing into a violent, highly destructive civil war
then, would possibly give the Germanic pagans somewhat better odds. It keeps the whole Frisian region (which covers most of the Low Countries at the time) conveniently Pagan, and prevents the Franks from militarily crushing the Saxons later on. You'd need then have the Saxons emulate Redbad, with some alt-Widukind coming to power and leading the pagan Saxon struggle against Christian encroachment.
Ideally, have the families of Redbad and alt-Widukind become united through marriage, and form further bonds with the Scandinavians. With the Franks defeated earlier, the Christian missionaries kept out, and the cultural identity based on the "Men of the North" having gloriously defeated the Christian Franks... Well. They'd be in a stronger position, and they'd have more time to set up a common cause. In this scenario, the Frankish realm really does end up only covering the region of France, and all of (Northern) "Germany" (including the Low Countries) stays pagan, as does Scandinavia.
This would be sufficiently early for this pagan Germanic realm to be well-defended against the Franks, and would leave the pagan Germans relatively free to carry out their very own Ostsiedlung. By the time the Christian realms really get into a position to come a-crusading, the pagan realm (particularly if it's fairly united) should be pretty big and pretty populous. Possibly able to hold its ground...