Complex sentence: In a naval battle in the Amur a few miles downstream from the mouth of the Sungari (July 10,1658), the 11-ship Russian flotilla is destroyed (the survivors flee on just one ship), and Stepanov himself dies.
Split into simpler sentences: In a naval battle in the Amur a few miles downstream from the mouth of the Sungari (July 10,1658). The 11-ship Russian flotilla is destroyed (the survivors flee on just one ship), and Stepanov himself dies.