Nieembucu

Nieembucu (Spanish: Ñeembucú), officially the Republic of Nieembucu (Spanish: República de Ñeembucú) is a small and irrelevant country that shouldn't even exist between Argentina and Paraguay in South America.

Argentine Civil War
The existence of this little country is because of three words: Argentine Civil War. Before it, Nieembucu (was still called with its Spanish name, Ñeembucú, in English back then) was a department of Paraguay. Then, in 1990, a civil war broke out in Argentina due to economic differences, with two sides, called Greater Argentina and Lesser Argentina. At one point of the civil war in 1991, Greater Argentina thought of an idea in Formosa (a Lesser Argentine province but it was occupied by Greater Argentina at that point). Insead of getting to Chaco, then Corrientes (both Lesser Argentine provinces but neither were occupied by Greater Argentina at that point), why doesn't she get Corrientes straight away? But how will she do that? The answer is that she will buy the Ñeembucú Department from Paraguay. So Argentina did it, and got Corrientes. Oh, and Ñeembucú joined Argentina and the Argentine Civil War on the Greater side.

Disputed Nieembucu
The civil war ended in 1992 with Greater Argentine victory. After the civil war, Paraguay asked "Argentina, now that your civil war is over, can I have Ñeembucú back?". But Argentina responded "NO! She helped me in the civil war, and I supported her too! But when she was yours, you did nothing to improve her! She's better off as mine!". At that point, Paraguay got really mad at Argentina that they both met up at Pilar (Ñeembucú's capital) to sign the Treaty of Pilar that makes Ñeembucú part of both Argentina and Paraguay at the same time, or in other words, disputed. Argentina thought it was hers, and Paraguay thought it was hers. Since this was a case of border dispute. Ñeembucú's name had to be adopted to English, but they couldn't due to the Spanish characters Ñ and Ú. So they replaced them with Ni and U respectively, making the territory's English name "Nieembucu". Don't worry about its Spanish name, its still "Ñeembucú". An independence movement started too.

Independence
After 7 years of being disputed, in 1999, Nieembucu decided to go independent, since they thought "Make Nieembucu fully neutral about Argentina and Paraguay. We need peace here. Best Nieembucu, independent Nieembucu." And A and P said "Yeah, we kinda agree. We were getting tired of this anyway." And in 5th of May 1999, the Republic of Nieembucu was formed. Argentina aided the new country for a bit.

Trivia

 * May 5th because I came up with this country on May 5th.