Original sentence: At the start of the war the Royal Flying Corps (RFC) in the Field, commanded by Sir David Henderson consisted of five squadrons – one observation balloon squadron (RFC No 1 Squadron) and four aeroplane squadrons (RFC No 2, No 3, No 4 and No 5 Squadrons)
Edited sentence: At the start of the war the Royal Flying Corps (RFC) in the Field, commanded by Sir David Henderson consisted of five squadrons—one observation balloon squadron (RFC No 1 Squadron) and four aeroplane squadrons (RFC No 2, No 3, No 4 and No 5 Squadrons)