On Friday, Czechia and Slovakia teamed up again, and while ignoring the Velvet Divorce, we and our brothers acted as one nation and we vetoed an EU document (mostly a document pushed by Bulgaria) on the accession of North Macedonia (and Albania) despite the fact that (and maybe because, as I will explain) both Czechia and Slovakia are arguably greatest supporters of the enlargement of the EU.
Skopje, North Macedonia
We're often talking about the incorporation of the Western Balkans into the EU. "Western Balkans" is the Western part of the peninsula and in practice, the phrase "Western Balkans" refers to the combined territory of (former) Yugoslavia and Albania – usually minus Slovenia (even though it was a part of Yugoslavia) because it's already far enough from the peninsula proper and politically tightly aligned with Austria.
The Balkans are complicated, explosive, and balkanized (i.e. fractally organized into minorities within minorities within minorities etc.). I have no doubts that the incorporation of the remaining countries into some European structures is good both for the prosperity and peace in these traditionally risky countries. But despite all the gibberish about the "EU that protects peace", we may see that the contemporary European Union is mostly a tool to revive the wars, in this case the Second World War.
You may read this Quora answer of mine and this one about the European countries that are not in the European Union. A motley crew, indeed. Here, we care about the post-Yugoslav countries. OK, Slovenia was the most Westernized post-Yugoslav country and this "Slavic country closely affiliated with Austria (like Czechia)" (but with a lot of history shared with Italy as well) easily won the independence from Yugoslavia and the EU membership. Croatia – a long-time Slavic ally of Germany (where fairy-tales about Croats' being Germanic Goths have always been popular although DNA indicates it was always BS) – joined a few years later.
What is left is Serbia and Montenegro (Montenegro is the closest post-Yugoslav country to Serbia and the separation of Serbia and Montenegro was recent and "optional"); Bosnia and Herzegovina; North Macedonia; and Kosovo (the cradle of the Serbian statehood that got filled with too many Albanians who recently succeeded in completely stealing the territory from Serbia). Albania was another independent country during the war – a highly isolated one, inaccessible even for us, the (distant) comrades.
Serbia (and Montenegro) aren't in the EU because of the Serbian-Russian links and the EU hatred towards Serbian leaders during the Yugoslav wars. But of course, I think that Serbia (and Montenegro) are completely ready to join the EU, are very stable and decent nations, and would be a positive contribution to the internal atmosphere in the EU. Bosnia and Herzegovina is a problematic land because it's a majority Muslim one; it is the "bulk of old Croatia up to the battlefront" that was taken by the Ottoman Empire (the Islamic Turks). I have some doubts about the adequacy of Bosnia and Herzegovina in the EU; the Islamic doubts also extend to Kosovo (a majority Islamic country) which also had the terrible leaders who were organized criminals and did organ trafficking and other things.
North Macedonia seems like the least problematic country in the Western Balkans that could be admitted to the EU.
Note that the Serbian language, Croatian language, Montenegrin language, and Bosnian language are basically the exact same language, Serbo-Croatian. The illusion of differences is a political construct. If you classify them as different languages, they are (even) far closer than Czech and Slovak. On the other hand, Slovenian is a sufficiently different, but also South Slavic, language. And Macedonian is different both from Slovenian and Serbo-Croatian but it is very close to Bulgarian (Bulgaria was the only country speaking a South Slavic language that wasn't incorporated into Yugoslavia, note that Yugoslavia means the South Slavic Land). Bulgarian and Macedonian are the only Slavic languages that have (the) articles in front of (the) nouns. (Well, one of them puts "to/ta" before the noun, the other after the noun.)
These days, Macedonia has about 2 million people. It's a small country in between three neighbors that would like to swallow it: Serbia, Bulgaria, and Greece. These countries have always spun the history and present in their own ways to justify the annexation (I use the harsh word "annexation" but of course the plan is always more gradual and seemingly milder and slower).
Concerning the language, as I said, North Macedonia is closest to Bulgaria. These are the Slavic languages with (the) articles. I will return to the "linguistics-based spin from Bulgaria" later because it's the key topic here. On the other hand, when it comes to the ancient political and historical roots, North Macedonia is closest to Greece. The North Macedonians have been the loyal Slavic inhabitants in the land that came from the Macedon Kingdom (the Southern part of which is a province in Greece); all Greek kingdoms were reinterpreted as parts of the Byzantine Empire some 1,000 years ago, the surviving "Eastern Roman Empire". Greece actually imposed this meme, "you are Macedonians just like many Greeks", in the 19th century efforts to control the (modern name) North Macedonian territories. It was crazy that the same nation of Greeks was fighting against the North Macedonian rights to use the name "Macedonia". The usage was imposed on North Macedonians by some other Greek nationalists just 100-200 years earlier!
And in the 20th century, especially when it came to the decisive world wars, Macedonia was affiliated with Serbia. This was reflected in North Macedonia's being a part of Yugoslavia for the bulk of the 20th century. In some geopolitical sense, that affiliation meant the Serbian control over North Macedonia. Of course I think that the Serbs were kind enough rulers in Yugoslavia who preserved a decent equality between the constituent nations – especially because the long-time communist leader Tito wasn't even a Serb.
Great. So three nations would like to promote their stories about North Macedonia's "de facto non-existence". Czechia and Slovakia happen to promote the fourth picture (which the bulk of Macedonians arguably support), namely an authentic sovereignty of North Macedonia that is neither a piece of Greece, nor a piece of Serbia, nor a piece of Bulgaria. Czechs and Slovaks naturally support nations that have to face the bullying by larger neighbors – for a simple reason, this description has often applied to us, too. However, there is something more important going on, and it's the efforts to revise the results of the Second World War.
The Second World War was a bloody conflict and it polarized and separated nations along an axis. On one hand, you have the "large enough nations that like to be bullies", that's the Axis around Germany and its regional allies and imitators; on the other hand, you have the nations that prefer a more international organization without "clearly dominant" players. That's the Allies.
This basic axis – and the memories of the Second World War – have never completely disappeared. They are reappearing often. Many recent conflicts were just 21st century proxies to the Second World War. Sadly, I think that the latest Bulgarian efforts are just another example of that.
Great. You must understand that Croatia was largely a pro-Hitler country during the Second World War (have you heard of Ustaše?); while Serbia was a key anti-fascist country with the dominance of partisans. Much of the Serbo-Croatian tension was a repetition of the Second World War; Croats tend to be pro-Hitler although they use nicer words now (of course they are close to us Czechs but they are politically much more distant from Russia, relatively to the Czech distance, than the longitude would indicate); Serbs are anti-Hitler. The preservation or restoration of Yugoslavia is anti-Hitler; various other reorganizations of the area that divide Yugoslavia to assorted pieces are pro-Hitler. It's because Yugoslavia, like Czechoslovakia, is a symbol of a "weak" alliance of several close enough nations that don't really rape each other. Do you get it?
As long as you keep North Macedonia as a part of the Serbian-led Yugoslavia (and that was the status in most of the 20th century), it's anti-Hitler. And indeed, the ethnic Macedonian tended to be anti-fascist. However, Bulgaria was sufficiently different. Up to 1941, Bulgaria was neutral but between 1941 and 1944, Bulgaria was aligned with the Axis! It was just three years but this period has explained the bulk of the spirit. (Some, not all) Bulgarians were the main pro-Hitler players in North Macedonia during the Second World War. Now, Slovaks were also more pro-Hitler on the axis than Czechs but the difference ends up being much smaller than the Bulgarian-Macedonian distance. After all, Czechs also had some fascists; and Slovaks had a powerful 1944 Slovak National Uprising against the clerofascist regime. The "totally different status" of Czechia and Slovakia during the war was partly a Hitler's construct, not necessarily a reflection of fundamental differences between Czechs and Slovaks. Slovaks looked more pro-Hitler than Czechs but their tension with the Hungarians was more lasting and the Hungarians were more pro-Hitler than the Slovaks which is what ends up being more important even today, when any hypothetical bitterness from the dissolution of Czechoslovakia is 100% gone.
Fine, so Bulgaria and North Macedonia are going through some mutual tensions right now – which may have overshadowed the Greek-Macedonian tensions just a few years ago. Bulgaria is the pro-Hitler player, North Macedonia is the anti-Hitler player. Bulgaria claims that North Macedonia is just a recent social construct, an unnatural appendix of Bulgaria that was just randomly dragged elsewhere. There is no separate intrinsic existence of North Macedonia as a construct, Bulgarians basically claim. You can imagine that when you're a patriot, the denial of the very existence of your nation is one of the most insensitive things that other nations may do to you. Of course sensitive (or experienced) enough people (and nations) know something about it. I do understand now why many Slovaks weren't terribly happy when most Czechs said "Czechia or Czechoslovakia, it doesn't matter, what's the difference?" and be sure that this is how almost all Czechs viewed the difference between Czechia and Czechoslovakia. Well, the difference between Czechia and Czechoslovakia is... Slovakia, and saying the difference didn't exist was basically equivalent to saying that Slovakia was equal to zero. It's not hard to understand that someone who likes his Slovak homeland could be annoyed by such a computational result, is it?
OK, in the same way, these particular Bulgarians feel self-confident enough and they claim that North Macedonia basically doesn't exist. It's just an offshoot of Bulgaria. What's annoying about this summary is that it is just a simplified meme randomly chosen from two similar ones which are mirror images of one another. What I want to say is that you may equally say that Bulgaria doesn't exist – it is just some extension of the Slavic Macedonia. Bulgarians don't really exist, they were just some Turkic buggers (therefore the name "Bulgaria") who weren't viable as a civilization, had to be given some know-how, and the know-how came from the Orthodox Christian Greece, but as the current Slavic Bulgarian language indicates, the Turkic tribes were first Slavonized and the know-how didn't come directly from Greece, it came through the Macedonians, the Slavic speaking citizens within some Greek kingdoms that were still around 1000-1300 years ago.
It should be clear to everybody that such stories are oversimplified, biased, one-sided pieces of propaganda. You just can't say that North Macedonia is just a tiny derivative of Bulgaria much like you can't reasonably say that Bulgaria is just a derivative of the Slavic Macedonia. If Bulgaria wants to abuse the Macedonian desires to be in the EU to play these games, it must be stopped.
Too bad, it was just Czechia and Slovakia that carefully guarded the actual Macedonian folks' interests – and we needed to slow down the accession talks a little bit. As I indicated, it's not just because of our role of nations that were repeatedly "smaller nations bullied by larger neighbors". The really dangerous point is that Bulgaria is restoring some pressures that existed during the Second World War. In 1941-1944, Bulgaria was a full-blown ally of Nazi Germany and its efforts to control the surrounding territories were analogous in logic to the efforts of the Third Reich.
As I have sketched, North Macedonia has much more independent history than what these pathetic Bulgarian simplifications indicate. They're descendants of loyal citizens of the Kingdom of Macedon, and its successors. And perhaps even more importantly, North Macedonia has had all this 20th century history within Yugoslavia (or the Kingdom of Slovenes, Croats, and Serbs). Bulgaria really wants to erase both from the history. The erasure of Yugoslavia as a part of the history that has co-shaped the North Macedonian national identity is clearly unaccceptable. It's a full-blown Nazi policy that always came together with the denial of the existence of Czechoslovakia. In this Nazi German perspective, and not only in this perspective, Czechoslovakia and Yugoslavia were obvious siblings. They were countries that were created as the cornerstones of the "new map of Europe" after the First World War in late 1918. Czechoslovakia was fully prepared in the international waters by our brilliant founders; less brilliant Yugoslavs copied everything one day later. ;-) But otherwise what we did was the same thing. The idea of a non-existence of Yugoslavia in the history; or the would-be irrelevance of this existence for the national identity of the component lands is clearly on par with Hitler's temporarily successful efforts to deconstruct Czechoslovakia.
I think that this is the rough analogy that is the main reason why Czechs and Slovaks had to veto the document on the enlargement. It would be a precedent that would encourage similar revanchist campaigns – to change the political balance, rewrite the history, and challenge the results of the Second World War in Europe which are clearly vastly more important for peace on the Old Continent than some European Union. (The story above makes it clear that the Second World War was just a modified, more polarized and more ideological, repetition of the First World War, with basically identical results. Czechs and Serbs were on the winning side in both wars; Germans, Austrians, and Bulgarians were on the losing side, ignoring the Bulgarian U-turn in 1944-45.) In the Balkans, it's Bulgaria that is playing the role of the (Central Powers and) the Axis; in Central Europe, it would be Hungary, Austria, and perhaps Germany itself. But the logic could be recycled immediately. We can't afford this distortion. North Macedonia (and perhaps Albania) in the EU would probably be an improvement; but the North Macedonians' right to exist without a direct control by the Bulgarians, Greeks, and Serbs (the latter haven't been aggressive since the 1990s, so it's the other two now!) is vastly more important for the well-being of the North Macedonian nation, and for the peace in the Balkans, than anything related to the European Union! Sadly, a big part of the contemporary Russophobia is just a recycled version of Hitler's Drang nach Osten, too. If and when the tension gets really war-like, you simply need to expect the Czechs (and very likely Slovaks) to take the Russian and Serbian side again!
The history mustn't be rewritten. And it's particularly important that larger neighbors mustn't be allowed to rewrite the shared history with their smaller neighbors, especially not if and when the larger neighbors have already gotten a lesson when they lost an important war.
P.S. Šimon's answer here also points out that Bulgaria called the Macedonian flag (a yellow Sun-disk with yellow-and-red rays around) a "ventilator". Bulgaria threatened an intervention meant to remove monuments whose history they don't like, denied the existence of Macedonia before 1944, and demands the phrase "Macedonian language" to be replaced with a contrived phrase "official language of North Macedonia", a replacement clearly meant to support the idea that North Macedonia doesn't really exist or is extremely unnatural, to say the least. In Bulgaria, the Macedonian language is presented as a dialect of Bulgarian.
OK, my story is a "modern variation of the topics of the First and Second World Wars" but in Macedonia, some pundits see our approach as an echo of the heritage of Saints Cyril and Methodius, the two Greek linguists from Thesalonike who brought the Orthodox Christianity to "Czechoslovakia" (Great Moravia) in 863. They mastered and refined the Slavic speakers' language from their home which could have been old Macedonian or old Bulgarian. Macedonia was a bit closer geographically and politically. Of course, the differences between Slavic languages of the mid 9th century were much smaller than today. The same Macedonian daily thanks Czechia and Slovakia in the main story. Another article quotes the Czech ministry in detail, one more is about the Slovak ministry. Of course, it's more fashionable to defend the views e.g. of 20 million brainwashed climate alarmist Germans. But to defend a nation of 2 million against EU-sponsored claims about the non-existence of their nation is the more important and ethical thing to do.