Headquarters and Service Battalion Marines attend the Seige of Petersburg Battlefield PME April 1 to promote morale and develop understanding of military history. The group also went to Fort Lee to learn about various MOSs produced there. - Headquarters and Service Battalion Marines attend the Seige of Petersburg Battlefield PME April 1 to promote morale and develop understanding of military history. The group also went to Fort Lee to learn about various MOSs produced there.