Answer:
Usually Field and Staff. Every regiment had ten companies, each commanded by a captain assisted by several lieutenants. Each company had one hundred men. Once assembled into a regiment the men would elect their "Field" officers - a colonel to command the regiment, and a lieutenant colonel as second in command, and a major. Staff officers were selected, including a quartermaster, a commissary, a regimental surgeon and so on. So, the Field and Staff were the headquarters group of a regiment; the personnel beyond those serving in one of its ten line companies.