Complex sentence: He returned to Britain in 1812, and in January 1813 was sent to inspect a Russo-German legion then being formed, and he accompanied the armies of the allies through the campaigns of 1813 and 1814, being present at thirteen important battles.
Split into simpler sentences: He returned to Britain in 1812, and in January 1813, was sent to inspect a Russo-German legion then being formed. He accompanied the armies of the allies through the campaigns of 1813 and 1814, being present at thirteen important battles.