ratovati

1. to wage war; to fight in a war
   Moj deda je ratovao u Drugom svetskom ratu. — My grandfather fought in World War II.
   Te dve zemlje su ratovale vekovima. — Those two countries were at war for centuries.
2. (with someone) to feud; to battle
   Već godinama ratuje s komšijama zbog parkinga. — He's been feuding with his neighbours over parking for years.

Used with s + instrumental or protiv + genitive.