Complex sentence: Originally formed in 1755 at Salisbury as the 56th Regiment of Foot, it was renumbered as the 54th Regiment of Foot when the 50th Regiment and 51st Regiment were disbanded.
Split into simpler sentences: Originally formed in 1755 at Salisbury as the 56th Regiment of Foot and renumbered as the 54th Regiment of Foot. It was renumbered when the 50th Regiment and 51st Regiment were disbanded.