Complex sentence: The first special police unit, the Lučko Anti-Terrorist Unit (ATU), was established on 7 September 1990 and its ranks were filled through selection of police officers trained Zagreb in 1990.
Split into simpler sentences: The first special police unit established in the 1990s was the Lučko Anti-Terrorist Unit (ATU). Its ranks were filled through selection of police officers trained Zagreb in 1990.