Complex sentence: It was fought between a British Royal Navy destroyer flotilla sortied to intercept a "Kriegsmarine" force of two corvettes and a destroyer sent to escort a German convoy retreating from Šibenik to Fiume (present-day Rijeka).
Split into simpler sentences: It was fought between a British Royal Navy destroyer flotilla and a "Kriegsmarine" force of two corvettes and a destroyer. The German flotilla was deployed to escort a convoy retreating from Šibenik to Fiume (present-day Rijeka).