Complex sentence: The right, or eastern, column was headed by the, followed by Hopkins' flagship, the, at 20 guns the largest ship of the fleet, and the left column was headed by the, followed by the.
Split into simpler sentences: The right, or eastern, column was headed by the, followed by Hopkins' flagship, the, which, at 20 guns, was the largest ship of the fleet. The left column was headed by the, followed by the.