Complex sentence: Macdonough relieved Isaac Hull of command on July 1,1815, and was placed in command of the Portsmouth Navy Yard for three years after which he returned to the Mediterranean Squadron as commander of the, a frigate bearing 44 guns.
Split into simpler sentences: Macdonough relieved Isaac Hull of command of the Portsmouth Navy Yard on 1 July 1815. In command there for three years, he returned to the Mediterranean Squadron as commander of the, a frigate of 44 guns.