Complex sentence: Joined the 31st Regiment of Foot in Bengal, India, where he greatly distinguished himself as a Lieutenant, under General George Pollock, in the war in Afghanistan, and wrote an account which was considered an authority on the campaign.
Split into simpler sentences: Joined the 31st Regiment of Foot in Bengal, India, where he greatly distinguished himself as a Lieutenant, under General George Pollock, in the war in Afghanistan. Wrote an account which was considered an authority on the campaign.