The Greek city-states habitually waged war on each other, so there were endless examples. They desisted briefly to face off the Persian intervention in thee Greek world in the 5th Century, but before and after that the cities had continual disputes and wars. The most intense was the 27-year Peloponnesian War 431 to 404 BCE which pitted Athens and its empire against the Peloponnesian League led by Sparta.
Sparta and Athens fought
From 1946 to 1949.
Greek Civil War happened in 1919-03.
Civil War Generals II happened in 1997.
Second English Civil War happened in 1648-02.
Sierra Leone Civil War happened on 1991-03-23.
Indian intervention in the Sri Lankan Civil War happened in 1987.
Greek War of Independence happened in 1821.
Somali Civil War happened in 1996.
Georgian Civil War happened in 1992.
Civil war in Tajikistan happened in 1993.
Paraguayan Civil War happened in 1947.
Uruguayan Civil War happened in 1839.
Liberators' civil war happened in -43.
Castilian Civil War happened in 1368.
Piedmontese Civil War happened in 1639.
Salvadoran Civil War happened in 1980.
Djiboutian Civil War happened in 1991.
Jementah Civil War happened in 1879.
Guatemalan Civil War happened in 1960.