Complex sentence: Upon successful completion of either school the Marines recieve the MOS of 0321 Reconnaissance man and go on to attend S.E.R.E School, Army Airborne School, and Combatant Diver school.
Split into simpler sentences: Upon successful completion of either school the Marines recieve the MOS of 0321 Reconnaissance man. He will then to attend S.E.R.E School, Army Airborne School, and Combatant Diver school.