Complex sentence: However, the rank of the appointment holder and the holder's appointment are separate; that is not all Lieutenant Colonels are CO's, and although most COs are Lieutenant Colonels, that is not a requirement of the appointment.
Split into simpler sentences: However, the rank of the appointment holder and the holder's appointment are separate. That is, not all Lieutenant Colonels are CO's, and although most COs are Lieutenant Colonels, that is not a requirement of the appointment.