Okay, the most sensitive topic:
The cultures.
Before I get into this topic i just want to share my personal view and experiences on the representation on cultures in Paradox games especially of the Hungarians.
In Hungary without any irredentistic or nationalistic view it is widely accepted that the Hungarians made up the absolut majority in the Carpathian basin during the medieval ages (without Croatia of course). Some estimations put the medieval Hungarians up to 70-75%, but I have read studies with 80-85% too. Obviously it's hard to tell, since the first census happened in 18th century, and these datas are only speculations mainly based on church documents on the numbers of the believers of different churches and based on toponyms + archaeological finds. Of course this doesn't mean that the whole Carpathian basin was lived by ONLY the Hungarians, the population's size could vary based on population density as well. So the Slavs could live from today's Western Slovakia to modern day Ukranie but the territory density was not as high as on the Hungarian plain so the slavic population is much more lower in numbers than it might seems on maps.
For example population density was the highest on the great Hungarian plains, in Transdanubia, between the Tisza-Danube, Transtisza region and in the Banat, until the Ottoman occupation of Hungary. This basically dropped the previous village density as well, as the average village density in 45km2 was 35-50 which dropped to 10-20 in some regions which is a really huge dropback. This process is known as "pusztásodás"/abandonification where many previous medieval villages are left abandoned, and were not resettled after the Turks were kicked out of the country, and the previous village now serve as an agricultural field. The Hungarian plains contain many of these medieval churches as messengers of the one stood medieval villages.
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A great example how a medieval village was not repopulated after the turks, and now only the church stands on the plains as the last remnants of the village.
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Needless to say this unfortunate historical event sealed the country's demographic fate as the high density territories were razed due to constent wars. And was also abandoned by the local population where the vast majority of the Hungarians once lived.
These inner pre-occupied by the ottomans territories were needed to be repopulated so other Hungarians from different bits of the country were resettled and other nationalities were resettled. This for example causing the Hungarian-Slovak language border to shrink further to the south, as the villages and cities left by the Hungarians were refilled with the local Slovak population. But also this is the case with the Partium, where the survived Hungarians were resettled on the central bits of the Hungarian Plains, and Transylvanian romanians were resettled in the Partium.
This was due the different offers and privilages as many local nobles offered reduced taxes or completely tax exemption for a few years if some peasant settled down on his fiefs. The ethnicity was really a secondary priority as the lands needed to be cultivate and the country was needed to be rebuilt.
So while playing with paradox games - like EU4 or Crusader Kings 2/3 it's no surprise when we Hungarians feeling left out of the discussions when it comes to the cultures of the Carpathian basin, and we are feeling that the Hungarians are way too underpresented in their own country, and other nationalities are overpresented (Serbians, Romanians mainly). This is mainly due to the fact that some people might think that the ethnical composition of the country hasn't changed, and some culture represantions are based on 19th century census dates which are nonsense of course.
Furhermore unfortunately there are many Paradox game streamers like Ludi himself, who tend to comment on these Tinto topics and he's spreading falsifications to his viewers especially of the history and the cultural composition of Translyvania. Indicating that romanians were always the majority in Transylvania, and the romanians are too underrepresented.
But this time it's not a post Ottoman period that needs to be represented in the game it's a pre Ottoman era, furthermore a time before the Black Death (if the 1337 starting date is really legit)
As others pointed out that after the arrival of the Hungarians the Hungarians found a local slavic population.
We can argue about the continuity of these slavic populations (white croats - ruthenians - ukranians, slavs to the south - serbians) (we also had this argument previously) but it wont change the historical records what came in the next few centuries.
In Transylvania's case the historians do agree that some sort of slavic population has lived in the region, probably the Bulgarians, who ruled the area for a few decades. Previous slavic migration also occured in the region, likely because of the North to South migration of slavs. So slavic toponyms can be found in the region - like "Kovászna/Covasna" from the slavic "kvas" which refers to the bitter spring water of the region. In Hungarian the "kovász" also means bitter or sour - like kovászos uborka (pickled cucumber) or kovászos kenyér / sour dough bread.
Also the river Cerna/Cserna in Transylvania of Slavic origin where "cerna" means black. The same etymology can be seen with the Hungarian city "Csongrád" which couldve been "Csernigrad" "Black castle" as it was a Bulgraian timber fortification and it really looked black.
A different toponym for the slavic presence in the region was preserved in the Romanian language as Bălgrad. This was the Romanian name for Gyulafehérvár before the artifical "Alba Iulia" was even a thing. Where the Iulia is a mistranslation of the hungarian name "Gyula" as many Hungarian believed mistakenly that it's the Hungarian form of the latin given name "Julius". Bălgrad itself means "white castle" as the modern day Serbian capital Beograd/Belgrad.
It's really common within slavic languages (and in Hungarian as well) that previous Roman settlements were named as "white castles" since the main building material of these cities were limestones and marble which really looked white. And both Beograd/Belgrad (Singidunum) and Gyulafehérvár/Bălgrad (Apulum) were important roman settlements.
(Also the fact that the Romanian language used Bălgrad - the slavic form of a roman settlement - further strengthens the theory that the Romanians are indeed not the descendants of the local romanized population since the roman settlement name "Apulum" was not preserved within the Romanians and the "Alba Iulia" which also a translation of "white" + "Gyula" is a modern term for the same city.)
Any further archaeological or written sources of any other nationalities in Transylvania are nowhere to be found.
It's still a debate how "slavic" were the local Bulgarians in Transylvania, (were they actually khazars, or turkic remnants) and did the Hungarians also settled down in Transylvania when they arrived to the Carpathian basin as some sources mentions the region before the term of "terra ultra silvam/Transylvania" as "Black Hungary". (Ungri Nigri).
Different studies have been made on the history of Transylvania especially of it's nationalities during the centuries since Trasylvania - until this day - causing tension between Hungarians and Romanians especially when it comes to the "who was first and when" question.
Let's just say toponyms are mainly reliable sources if you want to answer the eternal question.
On this topic István Kniezsa ethnic slovak-born linguist did many research, also he was the one who created the first 11th century ethnic map of Kingdom of Hungary mainly based on toponyms.
And since he was not an ethnic Hungarian himself I highly doubt that his researches were fueled by bias nationalistic/irredentistic Hungarian views.
It's also important to note that this map do contains it's errors where further researches refuted or corrected many of his beliefs.
For example - Beszterce/Bistritz/Bistrica is from the slavic "bistro" which means fast. As there are restaurants called "bistros" probably thanks to the Russian soldiers who in Paris wanted to eat something fast. - yet the city seems like a Hungarian-German toponym
Also Déva is more likely of slavic origin too, showed as a Hungarian toponym.
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Colors:
Pink - Hungarian
Blue - Slavic
German - Yellow
Purple - Romanian
This is only the map of his studies, his studies does referring to the transformation of different Hungarian sounds in Romanian of pure Hungarian origin.
Such as like the Hungarian "E" to Romanian "A" -
Erdély - Ardeal
Egyedhalma - Adjud
Egregy ~Agriju
And how the "VÁ" becomes "O" in Romanian
Temesvár - Timisoara
Segesvár - Sigisoara
(Nagy)Várad - Oradea
(Maros/Székely)Vásárhely - Osorhei (Targu Mures - also an artifical name for the city)
The map of the toponyms also coincides with the medieval nationalities of Transylvania.
Especially the purple areas to the south which are mainly from the county of Hunyad, and to the north which are mainly from the well-known "Mócföld"/Tara Motilor. "Tara Motilor" is considered as the oldest Romanian populated areas in Transylvania as in 1201 this territory was mentioned as Terra Blachorum. These lands were uninhabited by the local Hungarian population thanks to it's dense forests and hills. The toponyms here are mainly of Romanian origin which has no sense in Hungarian like "Nyágra"/Neagra.
This Romanian migration to "Tara Motilor" happened in a smaller scale compared to the others.
After the Mongol Invasion more people were needed to replenish the massacared population of Hungary. Different estimates tells that the Hungarians have lost 70-80% of their population on the Alföld which I think is a bit too exaggerated. Archaeologists excavated many sites during this time period and it is well researched.
Some of these 13th century villages were truly burn to the ground, and some site the killed local population was let to rot (this is known that the bones are not found in anatomical orders on many occasions), and at some places you find the desperate mother with her 2 kids hiding in the house oven while the mongols set her house on fire.
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The more accepted estimates put the population loss somewhere between 40-60%
Severe population losses also happened in Transylvania especially in Gyulafehérvár.
This was the reason why the Cumans were settled down in 1246 once for all in the central region of Hungary.
The mongol invasion also caused further migartion to Transylvania. More german settlers, and also more of the Romanian population (from Wallachia) were invited to Transylvania. This further migration of the Romanians to Transylvania during this time also coincides with the construction of the first Romanian Orthodox church in Transylvania, Demsus (by the location it is also the area which was colonized by the newly arrived vlachs in Transylvania firstly prior to Tara Motilor).
The first romanian orthodox church in Transylvania, Demsus. CC. 13th century
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The Mongol invasion was not the only medieval event that changed the ethnic composition of Transylvania. A hundred years later the great plague, the black death hit the continent.
Hungary was no exception of the great plague unfortunately approximately every 3rd-4th people of the population has perished due to the plague (1347-1351). This of course mainly affected the more urbanized regions but rural regions were affected heavily as well. Obviously this also further affected the ethnic composition of Hungary which led to further immigartions.
Spread of the Great Plague
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If we agree on the starting date (1337) then when it comes to the cultures in the Carpathian Basin we have to rely on the datas BEFORE the plague.
Recently some more maps were released to the public during this time period. Most of the well-known maps are usually representing the migration to the Carpathian basin after the Ottoman wars. However 2 maps were released one from the late 13th century (this is the closest to the 1337 starting date) the other one presenting the post-plague cultures of Kingdom of Hungary which can be deceiving.
This is a well known map for many of the Hungarians - this is the migartions to Kingdom of Hungary after the Ottoman wars. The ethnic composition on the map representing the 15th century.
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Released ethnic map from 1495, 140 years later the plague which also seems similar to the one posted above (Yet i think on the first map the Ruthenian population is waaay to overpresented)
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A different map of this time period before the plague, also it is more close to the 1337(?) starting date which makes this map more reliable. It is mainly based on local toponyms, archaeology, and historical records - some newly founded romanian settlement were mentioned this time around firstly in the 1200's, and also based on historical family names.
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Based on this map this is my proposition for the Hungarians:
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And I still believe that the Romanians-Serbians and Ruthenians are too overpresented during this time
So my further suggestions: The circled areas be absolute majority - Also further expanded Hungarian culture (red lines)
I think the presence of the Romanians in the Partium and in the Banat needs to be reduced as they migrated to that area in a larger scale after the ottoman wars.
The "mixed slav-hungarian" population at the Southern bits of modern day Slovakia is an error i think. Those territories were inhabited by the "ancient Hungarians" after the arrival of the Hungarians. You can find Hungarian burials in the region in great numbers from 900's. The remaining slavic population was probably assimilated by the local Hungarians at the end of the 12th century mostly completely and I hardly believe that Southern parts of modern day Slovakia had significant pre-slovak population at the time. Just based on how many new Hungarian/German toponyms appeared at the region. Also the further shrinkage of the population in modern-day Slovakia happened due to the Hussite wars (1420s) which caused the locals to migrate further down south to avoid the constant raiding. looting and killing.
Yellow: German majority
Red: Hungarian majority
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