Complex sentence: As Yugoslavia began to dissolve, Višnjić was serving a year-long tour of duty with the Yugoslav People's Army (JNA) but left and returned to Šibenik, where he joined the nascent Croatian Ground Army during the Croatian War of Independence.
Split into simpler sentences: As Yugoslavia began to dissolve, Višnjić was serving a year-long tour of duty with the Yugoslav People's Army (JNA). He left the JNA and returned to Šibenik, where he joined the nascent Croatian Ground Army during the Croatian War of Independence.