SUGGESTED EAST SLAVIC CULTURE/LANGUAGE SPLIT:
Russian linguists generally agree that Old East Slavic already had several dialect groups by the 11th-12th centuries; I found three main theories for the exact split. By the late 1300s, political developments had mostly cemented their status. They weren't a perfect match for the languages and dialects of today - not even mentioning the spread south and east - as there were additional demographic shifts after 1400 (especially around Velikiy Novgorod, Smolensk, and Belgorod). However, they provide a very good and decently convenient basis for the cultures, dialects, and languages in Project Caesar.
The three theories, as posited by the respective linguists, are:
1. Khaburgayev - southwestern (Halych-Volhynian), southern (Central-Eastern Ukrainian), central (modern Belarusian and Southern Russian), northwestern (Novgorod-Pskov), and northeastern (Vladimir-Suzdal)
2. Ivanov - southwestern (Halych-Volhynian and Central-Eastern Ukrainian), western (Smolensk-Polotsk), southeastern (Ryazan-Kursk-Chernihiv), northwestern (Novgorod-Pskov), and northeastern (Vladimir-Suzdal)
3. Zaliznyak - northwestern (Novgorod-Pskov) vs southern-central-eastern (everything else); according to him, there were regional variances within the second group as early as 11th century, but this was the primary split until the Novgorod-Pskov and Vladimir-Suzdal dialects started merging together around 1200; this would set Novgorod-Pskov dialects solidly apart from the rest but would not preclude the rest from being split into different cultures in Project Caesar.
I found a map of the first theory and edited it to include the second:
View attachment 1228501
This map also includes written standards; the Western - Old Russian differentiation is a consequence of Lithuanian conquests so it shouldn't affect cultures/languages by itself. However, the Novgorod written standard is actually relevant because it predates Lithuania (Zaliznyak mentions Novgorod dialect being very different as early as 1125, and almost certainly before that), so it can be used to differentiate cultures.
This makes for a total of six language zones; these can be merged and shifted as necessary to meet Tinto's standards of having certain linguistic zones. For simplicity, southern and southwestern can be combined into a single Ukrainian dialect. Individual cultures can be rearranged too; two possible changes stand out. First, Chernihiv Severian can be grouped with the rest of Ukrainian. Second, Turov-Pinsk Polesian can be optionally grouped with Belarusian; I don't think this is necessary, because 1) Belarusian and Ukrainian would be part of the same language anyway, while Severian and the Ryazan-Kursk group would not, 2) Ukrainian-Belarusian and Belarusian-Russian had large transitional zones, as is typical of a language that's rapidly falling apart, but the Ukrainian-Russian transitional zone was much smaller, so it makes far more sense to move Severian than Polesian, and 3) some Belarusian linguists consider the speech of Turov and Pinsk up to the early 1900s to not be part of Belarusian.
On a six-zone map, this gives us the following languages and dialects:
View attachment 1228515
(Apologies for the seam and the empty corner... I had to merge multiple maps together).
Ukrainian and Belarusian dialects would be part of Ruthenian, while Novgorodian, Muscovite, and Southeast Russian (probably needs another name) dialects would be part of Russian.
I think there are three good ways to break these into cultures: a minimalist version (just the six blocks, but Tinto has already broken three of these up), a middle version (close to Tinto's current breakdown with the addition of only a couple cultures that I think are necessary) and a maximalist version (with several additional cultures on top).
Middle version:
View attachment 1228517
Maximalist version:
View attachment 1228518
The borders between cultures generally follow the political and (our best guess for) linguistic boundaries of 1337; in a few cases, modern linguistic boundaries have been used as secondary guidelines.
The corresponding political division under Kyivan Rus, the linguistic basis, and the tags for these cultures would be:
HALYCHIAN:
Principality of Halych
Syan-Dniester-Pokuttia-Bukovina dialect subgroup of Ukrainian
Tags: Halych (primary)
Optional: RUSYN:
Ruthenians within Hungary
Rusyn
Tags: none
(this one has no primary tag but it's heavily divergent today to the point of being considered its own language and in popular demand on the Carpathia-Balkans thread)
VOLHYNIAN:
Principality of Volhynia
Volhynian-Podillian and Western Polissian dialects of Ukrainian
Tags: Volhynia (primary)
DNIPRO UKRAINIAN:
Principalities of Kyiv and Pereyaslav
Middle Dnieprian and Slobozhan dialects of Ukrainian
Tags: Kyiv (primary), Pereyaslav (releasable), Kaniv (releasable), Zaporizhia (releasable)
SEVERIAN:
Principality of Chernihiv (not including the parts that broke off around the Oka)
Eastern Polissian dialect of Ukrainian
Tags: Chernihiv (primary), Starodub-Siverskyi, Novhorod-Siverskyi, Trubchevsk, Rylsk
POLESIAN:
Principality of Turov-Pinsk (incl. Slutsk)
Central Polissian dialect of Ukrainian and parts of Southwestern Belarusian that were not part of Polotsk
Tags: Turov (primary), Pinsk, Slutsk, Dubrovytsia (releasable)
POLOTSKIAN:
Principality of Polotsk (incl. the parts that broke off)
Central and Northeastern Belarusian dialects
Tags: Polotsk (primary), Vitebsk, Drutsk, Minsk (releasable)
Optional: BLACK RUTHENIAN:
Parts of Principality of Polotsk that do not speak a Central or Northeastern Dialect; geographical region of Black Ruthenia
Southwestern Belarusian with some Yotvingian influence
Tags: Novohrudok (primary)
This one makes for a good addition because it crosses linguistic and regional lines and because Polotskian looks funny otherwise. It's currently part of Polesian, which is a bit of an odd fit.
SMOLENSKIAN:
Principality of Smolensk
Western subgroup of South Russian dialects (Bryansk, Smolensk, and Upper Dnieper)
Tags: Smolensk (primary), Vyazma, Bryansk, Fomin(?)
OKAN (or Verkhovian):
Upper Oka Principalities (formerly part of Chernihiv)
Central subgroup of South Russian dialects (Kursk-Orel, Yelets, parts of Kaluga and Tula dialects, transitional zone around Karachev (southwest of w-u and yakanye isoglosses))
Tags: Odoyev (primary, releasable), Karachev, Novosil, Kozelsk, Tarusa, Mosalsk (releasable)
RYAZANIAN:
Principality of Ryazan
Eastern subgroup of South Russian dialects (Ryazan, parts of Kaluga and Tula dialects (northeast of w-u and yakanye isoglosses))
Tags: Ryazan (primary), Pronsk
MUSCOVITE:
Grand Duchy of Moscow, Principality of Vladimir-Suzdal, Principality of Murom
East-Central, Kostroma, and (possibly) Torzhok groups
Tags: Muscovy (primary), Murom, Vladimir, Suzdal, Dmitrov, Rostov, Uglich, Mologa, Beloozero, Yaroslavl, Kostroma, Starodub, Nizhny Novgorod, Gorodets, Galich-Mersky, Yuriev-Polsky
Optional: TVERIAN
Principality of Tver (originated in 1246)
Torzhok group and Tver subgroup
Tags: Tver (primary), Zubtsov, Klin, Kashin, Rzhev
The point of this one is that the area around Tver has some of the most transitional dialects today that might not necessarily fit with Muscovite, and also Muscovite is already the largest culture and could reasonably be split. Additionally, it could include parts of Novgorod that don't fit into the northwestern dialect group.
NOVGORODIAN:
Duchy/Republic of Novgorod
Northwestern dialect group using Old Novgorodian written standard and not subject to 14th-century Pskov-area phenomena such as yakanye; parts of Northern Russian dialect (which included Novgorod before some forced relocations by Muscovy)
Tags: Novgorod (primary), Oreshek
PSKOVIAN:
Duchy/Republic of Pskov
Northwestern dialect group not using Old Novgorod written standard and subject to yakanye and other southern/transitional phenomena; modern Pskov and Gdov groups
Tags: Pskov (primary), Toropets
Yes, I think this one should be included - the area roughly south of Pskov - Vyshniy Volochyok line was developing many new features at this time that weren't present north of the line near Novgorod and was already diverging rapidly (akanye dates to the 14th century, for example). It also makes sense to represent a political division between Pskov and Novgorod.
POMOR:
Novgorod's colonies off the coast (off-map)
No direct linguistic basis; area of secondary language formation (that is, an area that's liguistically mixed due to being recently moved into)
Tags: none