The Catholic Slavic nations use the Latin alphabet: Poles, Czechs, Slovakians, Slovenians and Croatians.
Yes, and everyone uses different versions of the Latin alphabet, these written languages do not mutually coincide. I don't quite understand why. Especially difficult is the fact that diphthongs and triphthongs are not similar to English, so it is difficult to read Polish roadnames (Czechs for sibilant consonants do all sorts of squiggles over the letters).
But this is writing, it can be anything. There is for example a Latin alphabet for the Russian language, the so-called "telegraph". I used to work with it when I was young.
But it's about the proximity of languages. The Polish pronunciation is very different from Russian, but my friends who have lived in Poland for a long time, said that in a month you get used to it, you begin to learn the words. Many words differ in the replacement of letters, for example, in Polish "rz", in Russian it is "r". "Andrew" - "Andrzej".
Czech - yes, it is the most different language. Slovaks understand it because they have lived in a common state for a long time. I once bought a book about hunting in a Czechoslovak bookstore and immediately bought a dictionary. But it turned out that the book is in Slovak, and the dictionary is Czech. It took me a long time to figure it out.
By the way, an anecdote about the Czech language: "the medical commission checks the immigrant. The optometrist shows a line on the table: "read this: CZRHS". Subject: "Oh, I know this guy!"
This topic is quite political. Both world wars began with an attack on the Slavic countries. This is not for nothing. The modern west-east conflict is rooted in long-standing events. The problems there began when Russia began to liberate those Slavic and Orthodox countries that were under the rule of the Turks (in the 18th century). The Europeans thought,
"These Russians are already too f...ing many, and what will happen if they join the Slavs, who are close to them in blood and language?".
And Austria was worried about its Slavic provinces, although historically it was often an ally of Russia. So some modern events are rooted in those times.