It’s often said that a language is simply a dialect with an army, and that couldn’t be more true in Europe, which in the fairly recent past saw the rise of nation states come with a corresponding rise in the ideology of national languages – an effective way to unify a group of people while strengthening and accentuating their differences with the people of the country next door.
Take Macedonian and Bulgarian, for instance. While in Ottoman Empire times, the people of this mountainous region (including what is now northern Greece and Serbia and other surrounding areas) spoke dialects of South Slavic that would have changed gradually from village to village (called a dialect continuum) so that neighbours could communicate easily but those from the farthest east and west would have had more difficulties, the development and codification of national Macedonian and Bulgarian languages created two separate entities – differences emphasized partly because literary Bulgarian was created with emphasis on the eastern part of the country – and corresponding national identities. Linguistic similarities and differences were (and still are) manipulated for political reasons, and local dialect differences gradually pushed aside in favour of the homogenous national language.
It’s something that has happened all over Europe, so that if you look at a map of majority language by region, it corresponds very nicely with national boundaries. But check out this gorgeously crowded map of the continent with priority “given to dialects and indigenous minority languages”. It paints a very different, and – if you ask me – much more interesting picture. (Above I’ve excerpted just the Macedonia/Bulgaria chunk of the map – click through to see the whole thing.)