Complex sentence: He took command of the armed frigate HMS "Tagus" in the Mediterranean Fleet in August 1815 and then the first-rate HMS "Prince Regent", as flag captain to Sir William Parker who was commanding on the coast of Portugal, in 1830.
Split into simpler sentences: He took command of the armed frigate HMS "Tagus" in the Mediterranean Fleet in August 1815. He was given command of the first-rate HMS "Prince Regent", as flag captain to Sir William Parker who was commanding on the coast of Portugal, in 1830.