An Army first sergeant is usually the senior non-commissioned officer (NCO) of a company- or artillery battery- or cavalry troop-sized unit. As far as pay grade, she's an E8, and only an army sergeant major ranks higher. Duties and responsibilities of a first sergeant are highly varied and can be complex. Outstanding leadership abilities are a must. As well, he must also be a very good administrator and manager. He's also the company commander's right-hand man.
The origins of Army first sergeants can be traced back to the Revolutionary War. Back then, they were responsible for enforcing discipline among the Continental Army's enlisted troops. George Washington installed them into units at the urging of Prussian General Baron Von Stueben. In fact, this new first sergeant position was based on the General's experience with the Prussian equivalent, the feldwebel. Newly created Army regulations then permanently codified the position of the Army first sergeant.
First sergeants, being E8s, serve as master sergeants when they're not officially designated as a company's senior enlisted leader. A master sergeant is inferior in rank to the First Sergeant as well, though both are actually have same pay grade. Master sergeants move laterally into the position when selected by the Army and the company's battalion-level leadership. Newly selected first sergeants also must attend a special 35-day training course before reporting for their initial duty assignment.
Within the company, first sergeants are responsible for the professional development of the non-commissioned officers below them. Additionally, this means they work hard at developing NCO leadership competencies. First sergeants are also usually the first step in the process that leads to nonjudicial punishment for wayward misbehaving soldiers. These senior sergeants are expected to know and apply applicable Army regulations in many different circumstances. They keep commanders apprised of all changes to those regulations, too.
Company commanders rely heavily on first sergeants to maintain order and discipline within the unit. These high-ranking enlisted soldiers are expected to lead from the front. This means they set the standard in terms of professional competency, uniform standards and physical fitness. They meet regularly with the command sergeant major and support her goals for the enlisted soldiers within the command itself. A poorly performing first sergeant can negatively affect his unit in a serious way.
There's a reason why a first sergeant is often referred to as "Top" or "Top Sergeant." Many times, she's usually entrusted by the company commander with some of the most important duties in a company. A good first sergeant is also a mix of disciplinarian and professional counsellor. Equal competence in office administration as well as field operations is demanded of him. He's the company's top enlisted leader in every regard.