Complex sentence: On 12 September 1990 he joined the Lučko Anti-Terrorist Unit, a unit of the Croatian police, and in 1991 it was used to deal with early incidents which developed into the Croatian War of Independence.
Split into simpler sentences: On 12 September 1990 he joined the Lučko Anti-Terrorist Unit, a unit of the Croatian police. In 1991 it was used to deal with early incidents which developed into the Croatian War of Independence.