Complex sentence: In 1581, the force besieged Pskov, a well-fortified and heavily defended fortress but with financial support from the Polish parliament failing, Batory failed to lure Russian forces in Livonia out into open field before the onset of winter.
Split into simpler sentences: In 1581, the force besieged Pskov, a well-fortified and heavily defended fortress. However, financial support from the Polish parliament was dropping, and Batory failed to lure Russian forces in Livonia out into open field before the onset of winter.