Stalin claimed that he liberated "Western Ukraine" - including the city of Lviv - from Poland in September 1939.
His basis for that claim was a notion, that this land used to be part of Medieval Rus before it was conquered by Poland in 1340.
However, Medieval Rus was - allegedly - founded by Varangians who were from Sweden.
So maybe it was in fact liberation of "Southern Sweden", not of "Western Ukraine" ???
In fact, the city of Lviv never belonged to Ukraine before 1939, so how could it be "liberated" as part of "Western Ukraine" ???
I would say, that Stalin in fact "liberated Southern Sweden" (or "Northern Austria" - but surely not Ukraine) from Polish "occupation".
But why was later Southern Sweden / Eastern Poland / Northern Austria left within the borders of independent Ukraine in 1991 ???
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Coming back to serious discussions:
Domen said:
So at first clans formed into tribes, and clan differences started to disappear. Then tribes formed into nations.
Here is, for example, something on how the Croatians and the Serbians formed:
And excerpt from Zofia Kurnatowska's book "Słowiańszczyzna Południowa" ("Lands of Southern Slavs") - translated to English:
"Ethnic and cultural environments
In discussed timeframe [9th - 10th centuries] initially quite homogenous culture of Southern Slavs undergoes some kind of differentiation. Centers of solidifcation appear, which are nucleuses of later Southern Slavic nationalities. Their coming into being was caused to a large degree by certain political-cultural conditions and to a lesser extent by processes of differentiation of Southern Slavic languages. (...)
Inhabitants of western part of the Balkan Peninsula, Serbian and Croatian tribes, were divided by quite negligible linguistic differences. What decided about their separate progress and about coming into being of different nationalities was the development of two distinct state organisms in those territories and their connection to two different Church centres (western in case of Croatia, eastern in case of Serbia). Croatia was initially limited only to territories located in the hinterland of the coasts of the Adriatic Sea. The expansion of the name Croatia into territory of Slavonia had, as has been underlined in historiography, a rather political than ethnic character. The issue of Serbia is more complicated. There is lack of exact information regarding the original territorial extent of Serbian tribes. Basing on tradition written down by Porphyrogennetos (but is it credible?) we classify as Serbians a number of tribes from southern Dalmatia (Trawunians, Zachlumians, Konawlans, Pagans-Nerentans), and first of all inhabitants of parts of Raška and Bosnia located "behind the mountains". Mysterious is the issue of the basins of Vardar and Morava rivers. Serbian ethnic center became more meaningful during further centuries, in period of heyday of the Medieval Serbian state. The unity of Serbian territory was strengthened by independent organization of its Church (at first an autocephalous bishopric, later a patriarchate).
Most of the Balkans were affected by Byzantine influences and belonged to the Orthodox Church, which however allowed for the development of native Slavic culture here. Only Croatia and part of coastal Serbia, as well as Slovenia, were tied with the Western Church and affected by influences of the Latin culture. (...)"
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So Serbian tribes and Croatian tribes were initially very similar peoples, who spoke similar languages.
They became two different nations - rather than one - because two different countries developed in territories inhabited by those tribes. Another factor which contributed to their differentiation were different cultural ties - Serbia was tied with Byzantine Orthodoxy, Croatia with Latin Western Christianity.
So within modern construct of a "nation-state", originally - in most cases at least - nation was the product of state, not state the product of nation.
Only in the 20th century people came up with an idea, that borders of states should be drawn along the borders of nations - not inversely.
In tribal reality - before nations were formed - the formation of nations was - in most cases - initiated by the formation of countries.
I know all of this may sound like "stating the obvious".