Complex sentence: They fought in the Napoleonic Wars (1803--1815), mainly around the Mediterranean, and were based in Malta and then in Egypt from 1801 to 1803, fighting in Sicily and Naples.
Split into simpler sentences: They fought in the Napoleonic Wars (1803--1815), mainly around the Mediterranean. They were based in Malta and then in Egypt from 1801 to 1803, fighting in Sicily and Naples.