So, let's say he decisively wins the battle of Stamford bridge, kills Harold Godwinson. Then he defeats William the Conqueror in battle. What would occur? Would he occupy England for himself or give the throne to Tostig? If he had conquered England what would change?
Oh, he's definitely not going to give Tostig the throne! That lackwit is going to be lucky to get Northumbria back; should he survive Stanford Bridge, I suspect Harald finds a nice backwater Earldom for the upstart Godwinson. Tostig's support would have been essential to Harald's assumption of the throne, but its also hard to deny the fact that he's highly unpopular in Northumbria itself (it rebelled against him, I believe, twice) and he was also willing to betray his own family in order to get revenge. Not the type of guy you give a huge, and influential, tract of land to!
Harald will likely rule directly from London. He had already given his sons Olaf and Magnus the joint Kingship of Norway before leaving on his expedition. I suspect that, should Harald take the throne of England, he might recall Olaf and rely on his support in administering the new land, leaving Magnus II in control of Norway. Now, in OTL, Magnus fell ill and died in 1069; I'm not sure if he was sickly by nature but, assuming he still dies around the same time, Olaf will become Harald's sole heir and eventually rule over both Kingdoms (this would have some major impacts on both England AND Norway. In OTL Olaf was known as a city builder and, in the ATL, I can see him enlisting English colonists to set up cities in Norway. This is going to tie those two nations even tighter through trade and culture).
The big question, of course, is how long Harald would live. He was only 51 when he was killed in battle, so its possible he might be able to live for another decade or so, baring illness or unforeseen events. This would give him enough time to truly secure his power in England and cement the control of his dynasty there. Now, assuming an orderly transition of power from Harald to Olaf, I suspect that House Hardrada is going to be primarily based in England. Olaf will likely split England and Norway between his sons, assuming he has two or more viable heirs.
Now, on the marco-level, we have an England where Northumbria and York are not depopulated by the Harrying of the North. The cultural shock of a Norwegian ruling House is also going to be much more muted than that brought about the Norman Conquest in OTL; England already had a Scandinavian ruler under Knut and the Anglo-Norse lords in the North will probably welcome the change. Furthermore, I suspect that Harald is more likely to make local allies and not rely on upturning the entire upper class as William did when he brought the Norman lords over. England probably remains more focused on the North Sea and the Scandinavian world (although its interests in the Lowlands trade networks will involve it in continental affairs, I certainly don't see it being drug into the French cultural and political sphere). Meanwhile, Norway likely ends up with some sparkling new trade cities which are settled partially by Englishmen. This is going to give the Norwegian economy a huge boost, and might be enough to make it the dominant Scandinavian country. If so, Harald, Olaf and future heirs are going to find themselves coming into conflict with Denmark sooner than later and possibly also Sweden.
So, Harald lives for a decade cementing his rule in England, dies, gives the throne to Olaf. I'm imagining a great change in "English" culture. Assuming the Norwegians hold England for a few hundred years (aside from Anglo-Saxon rebellion they really don't have any threat to their power in England) would we see a united Norse-English culture (In England, Norway would presumably just remain 'Norwegian')? Similar to how English culture changed under the Normans, with the induction of thousands of French words into the lexicon.
IOTL Norway and Scotland were rivals in the North Sea (which brings to mind images of Macbeth Act I), with England under Norwegian control would they eventually go to war with Scotland? I can't imagine Scotland winning in the long run, nor can I imagine France intervening (as opposed to IOTL where England had continental territory whereas Norway is not a threat/rival to France), so would all of Great Britain eventually fall under Norwegian control? It seems almost inevitable though I'm not sure about Ireland. I imagine this Norse-British state would have great colonies in North America. After all, Greenland and Iceland already serve as a base of operations into the New World, and a lack of continental interests might push Britain-Norway to look for a strong Royal Navy earlier on as the channel is not English on both sides.
I think they would both influence each other, however I think the Norwegians wouldn't adopt English, why should English become a prestige language? I think English as a Germanic language would revert to more Germanic roots and perhaps lose a good amount of its (limited) Celtic influence, and perhaps take in more Scandinavian grammar and vocabulary. I only know a little bit of Danish, so I can't really theorize what this could have led too vocab wise.I had actually forgotten about the Norwegian/Scottish rivalry over the northern islands; so, yes, I think its safe to assume that England/Norway will likely be drawn into conflict with them. I wonder if a Danish/Scottish alliance would end up developing to help counter them.
Although I do think Norwegian would have an influence on the English language, I don't think it would be nearly as widespread as the impact French had in OTL. In OTL, French was seen as the more prestigious language than English and was closely aligned with the governing class. In the ATL, I actually suspect that the roles might be reversed. If Olaf uses the English to help form settlements in Norway the language of administration in those cities would likely be English. This would mean that English would become the prestige language and would start exerting a major influence on Norwegian.
I think they would both influence each other, however I think the Norwegians wouldn't adopt English, why should English become a prestige language? I think English as a Germanic language would revert to more Germanic roots and perhaps lose a good amount of its (limited) Celtic influence, and perhaps take in more Scandinavian grammar and vocabulary. I only know a little bit of Danish, so I can't really theorize what this could have led too vocab wise.
So, Harald lives for a decade cementing his rule in England, dies, gives the throne to Olaf. I'm imagining a great change in "English" culture. Assuming the Norwegians hold England for a few hundred years (aside from Anglo-Saxon rebellion they really don't have any threat to their power in England) would we see a united Norse-English culture (In England, Norway would presumably just remain 'Norwegian')? Similar to how English culture changed under the Normans, with the induction of thousands of French words into the lexicon.
I think we'd end up ITTL with far more Norse words, and maybe also the way Norse languages indicate a plural or definite article at the end of the word which would be very interesting.There was already a great deal of Norse influence in English culture and language from the Danelaw, the Anglo-Saxon language borrowed a lot of Old Norse words. See "The History of the English Language Podcast". Yes, there are a lot of early French words in English, but most of them are alternate words for the same thing the Anglo-Saxon base language or the Norse borrowed words were. An example is the Anglo-Saxon derived 'cow' and the French-derived 'beef'. Probably the most important thing that Old Norse did for what would become English was to mostly eliminate the inflections that Anglo-Saxon used.
See also https://en.wikipedia.org/wiki/Old_Norse#Relationship_to_English
Three questions:
1. Just because William is defeated, what's to stop future Norman/Breton/French would-be conquerors from trying to invade again?
2. Why didn't the Norse try invading again IOTL after Hastings?
3. Just why was 1066 such a perfect storm for not one but two potential foreign claimants to invade and subsequently alter Anglo-Saxon culture for all time? Was Edward the Confessor just that big of a bonehead.