Complex sentence: Finaly, in 1455 the city of Peć fell in Turkish hands and the Serbian capital of Smederevo fell in 1459, marking the end of the main Serbian medieval state.
Split into simpler sentences: Finaly, in 1455 the city of Peć fell in Turkish hands. Soon after that, the Serbian capital of Smederevo also fell in 1459, marking the end of the main Serbian medieval state.