Complex sentence: Bjelovar is not an ancient town of Central Croatia; it was first mentioned in 1413 and only gained importance when a new fort was built there in 1756, at the command of the Habsburg Empress Maria Theresa.
Split into simpler sentences: Bjelovar is not an ancient town of Central Croatia; it was first mentioned in 1413 and only gained importance when a new fort was built there in 1756. It was built at the command of the Habsburg Empress Maria Theresa.