Complex sentence: Another form of rivalry within the United Kingdom is with certain forces of the Cadets; the Sea Cadet Corps, the Army Cadet Force, and the Air Training Corps; and between the Coldstream Guards and the Grenadier Guards, over the issue of seniority.
Split into simpler sentences: Another form of rivalry within the United Kingdom is with certain forces of the Cadets; the Sea Cadet Corps, the Army Cadet Force, and the Air Training Corps. Between the Coldstream Guards and the Grenadier Guards, over the issue of seniority.