What would be the effects of a Slavisiced Hungary?

Depends when it happens and what happens.
Do you mean an already established Kingdom of Hungary that would be slavicized, or Slavic domination over Pannonian Plain?
 
The former.
I don't see it happening, to be honest. Magyars pretty much took over slavic principalities and the remaining of Avars and Bulgars and assimilated them (critically by adopting a sedentary/agricultural life by the Xth) before establishing a kingdom in the early XIth century, with the era of great slavic migrations being already over at this point.

Eventually, Pannonian Plain wasn't slavicized enough to see Hungarians turning as Bulgars IOTL.

That said, having Hungarians not christianizing as quickly they did IOTL, may see a lesser assimilation of Slavic peoples that would see Christianity as a linguistical (trough slavonic) and cultural identitarian marker.
But, without Christianisation, you won't really end up with a kingdom of Hungary in first place.
 
I don't see it happening, to be honest. Magyars pretty much took over slavic principalities and the remaining of Avars and Bulgars and assimilated them (critically by adopting a sedentary/agricultural life by the Xth) before establishing a kingdom in the early XIth century, with the era of great slavic migrations being already over at this point.

Eventually, Pannonian Plain wasn't slavicized enough to see Hungarians turning as Bulgars IOTL.

That said, having Hungarians not christianizing as quickly they did IOTL, may see a lesser assimilation of Slavic peoples that would see Christianity as a linguistical (trough slavonic) and cultural identitarian marker.
But, without Christianisation, you won't really end up with a kingdom of Hungary in first place.

According to Wikipedia, the Mongol invasion killed half of Hungary's population. What if they stayed longer and massacred a much larger percentage of the population? Of course, this might have lead to Germanization rather to the area becoming Slavic, but I would assume that this would be important for the future language of the area.
 
What if they stayed longer and massacred a much larger percentage of the population?
Mongols didn't exactly slaughtered for shit and giggles, but as part of their warfare. Would have they remained longer, it would probably have stabilized.

Of course, this might have lead to Germanization rather to the area becoming Slavic, but I would assume that this would be important for the future language of the area.
A more important Germanisation is always possible, but I think you'd have enough of an Hungarian base to still have a largely Maygar Hungary.
Admittedly, it could easily looks more like a Transylvanian-like situation, with several ethnical/linguistical groups.
 
According to Wikipedia, the Mongol invasion killed half of Hungary's population. What if they stayed longer and massacred a much larger percentage of the population? Of course, this might have lead to Germanization rather to the area becoming Slavic, but I would assume that this would be important for the future language of the area.

Them staying longer might not do it, but a Mongol victory in Hungary coinciding with a Mongol DEFEAT in Poland, followed by Poland 'freeing' Hungary, might lead to a much heavier West Slavic (Polish/Czech/Slovak) presence. The extra prestige of being the conquerers/liberators might lead some cultural conversion (Magyars starting to speak 'Polish'), plus there might be settlement from the Polish lands.

Now, the Polish army and immigrants are likely to be heavily from the south (closest to Slovakia in location and dialect), and heavily leavened with Slovaks picked up on the way south. Thus, the Slavic language might be CALLED Polish (which is why the quotation marks in the paragraph above), but be closer to what we'd think of as Slovak. And that with a heavy Magyar infusion.
 
Them staying longer might not do it, but a Mongol victory in Hungary coinciding with a Mongol DEFEAT in Poland, followed by Poland 'freeing' Hungary, might lead to a much heavier West Slavic (Polish/Czech/Slovak) presence. The extra prestige of being the conquerers/liberators might lead some cultural conversion (Magyars starting to speak 'Polish'), plus there might be settlement from the Polish lands.

Now, the Polish army and immigrants are likely to be heavily from the south (closest to Slovakia in location and dialect), and heavily leavened with Slovaks picked up on the way south. Thus, the Slavic language might be CALLED Polish (which is why the quotation marks in the paragraph above), but be closer to what we'd think of as Slovak. And that with a heavy Magyar infusion.

In this case than most of southern Hungary would probably speak some form of Croatian.

----

Incidentally, there was an aborted TL about a more sucessful Croatian Kingdom in the pre-1900 forum where Croatia encompassed most of the Hungarian Plain (and beyond), so a Croatian Kingdom-wank could fulfill the OP's request: prevent the Croat Kingdom from going into a personal union with Hungary in 1102., and then after the Mongols invade and leave have Croatia expand northwards.
 
In this case than most of southern Hungary would probably speak some form of Croatian.

----

Incidentally, there was an aborted TL about a more sucessful Croatian Kingdom in the pre-1900 forum where Croatia encompassed most of the Hungarian Plain (and beyond), so a Croatian Kingdom-wank could fulfill the OP's request: prevent the Croat Kingdom from going into a personal union with Hungary in 1102., and then after the Mongols invade and leave have Croatia expand northwards.

Hmmm... Interesting idea.
 
Top