Q: Niko speaks Serbian, Why isn't his nationality stated in the article?

Niko is a fictional character. The author of the character is Dan Houser/Rockstar. Niko's nationality has never been divulged by Houser/Rockstar. Just speaking a certain language doesn't imply nationality of that country.

Q: Why does it say "A war in Eastern Europe"?

Niko is a fictional character. The author of the character is Dan Houser/Rockstar. The name of the war that their character took part in has never been divulged.

Q: But Niko's Nationality/the war name is obvious!

Because Niko is a fictional creation of Dan Houser/Rockstar, and they have never revealed any of this information, Wikipedia uses the most exact information that they have released. i.e. We don't know Niko's nationality. We only know that the war took place in "Eastern Europe". Anything else, such as stating Niko's nationality because he speaks a certain language, fall foul of WP:OR and/or WP:SYN.

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