A corporal in the armed services is a non-commissioned officer or an E-4. This rank is earned through time in the military branch, periodic tests and demonstrated capability at a military occupational specialty. Reaching the rank of E-4 or corporal brings with it duties and responsibilities to the ranks below.

Leadership

Corporals are the lowest-ranking NCO in the military unit, but it does place them in a leadership role. Each platoon is broken up into squads and then teams of four to five soldiers. A corporal leads either the squad or the team, depending on the number of corporals in the platoon. This leadership role makes the corporal responsible for the care and conduct of the soldiers under his supervision. This leadership role is maintained on the battlefield and off the field in the garrison.

Training Duty

Corporals train the soldiers under them. This training involves battlefield situations or advanced MOS training. In the Marine Corps, the corporal shows the lower-level ranks how to make a formation, what equipment is required and how to properly dress in garrison and on the battlefield. This is one of the primary responsibilities of the corporal to ensure the soldiers under him are prepared for combat operations.

Safety Duty

Corporals ensure the soldiers are properly equipped with water, food and safety gear such as helmets or body armor. This includes making sure the soldier is not sick or injured, which weakens the unit's effectiveness. The corporal must know where his soldiers are at all times, direct their movements on the battlefield and inspect their person and equipment on a periodic basis.

Communications

The corporal communicates with the soldiers assigned to him the policies and procedures of their unit's commanders or platoon sergeants. The corporal also communicates the readiness and capabilities of his assigned soldiers to superiors. This includes the health of each soldier, supply requirements and any other need to ensure the unit is prepared for any situation.