Complex sentence: The Siege of Novo Brdo was a military blockade of Novo Brdo, an important fortified mining town in the Serbian Despotate, by the forces of the Ottoman Empire, beginning in 1440 and lasting until the capture of the fortress on 27 June 1441.
Split into simpler sentences: The Siege of Novo Brdo was a military blockade of Novo Brdo, an important fortified mining town in the Serbian Despotate, by the forces of the Ottoman Empire. The siege began in 1440 and lasted until the capture of the fortress on 27 June 1441.