The United States Marine Corps Officer Candidates School (OCS) is the entry-level training for Marine officers, equivalent to recruit training for enlisted Marines. Located at Marine Corps Base Quantico, the school trains, screens, and evaluates potential Marine Corps officers. Unlike the other United States military services, the majority of Marine Corps officers complete OCS to earn a commission; the exceptions are midshipmen from the United States Naval Academy, limited duty officers, and inter-service transfers. Depending on the course, Officer Candidates go through either a 10-week (PLC Combined/OCC), or two 6-week courses (PLC) over separate summers, designed primarily to screen and evaluate candidates' fitness to lead Marines by placing them in leadership positions in a stressful environment. Students are evaluated during 2-3 day garrison command billets at the company and platoon level, and squad and fire-team level tactical billets during field exercises.