Complex sentence: Although the lineage date of the present regiment is 12 April 1808, on 3 March 1791 Congress added to the Army a Second Regiment of Infantry to aid in combating Indian attacks in the Northwest Territory.
Split into simpler sentences: Although the lineage date of the present regiment is 12 April 1808, the regiment's history actually begins in 1791. It was on 3 March 1791 that Congress added to the Army the Second Regiment of Infantry to aid in combating Indian attacks in the Northwest Territory.