The Battalion S-3 is the staff officer responsible for the operational and training plans of the unit. S-3s report to the battalion commander. S-3s generally hold the rank of captain and have been in the service for at least three years. This position is a key assignment because the S-3 works with other staff officers to develop training exercises and operating procedures.

Developing Training Exercises

S-3s are in charge of developing and administering training programs. When they learn from the commanding officer what the unit standards are, S-3s develop a training plan, determine which resources are necessary to complete the training exercises, conduct inspections, maintain readiness reports for each unit in the battalion and , if necessary, determine which soldiers will be sent to external training schools ("Air Force: Commander's Battle Staff Handbook," pg. 57).

Developing Operational Plans

The S3 uses information generated by the S-2 (security and intelligence) officer to formulate specific plans given the characteristics of the mission and the battalion's Area of Operation. For example, if the commanding officer of an infantry battalion directs the S-3 to develop a mission plan for capturing an insurgent leader, the S-3 will first consult the S-2 for information about the leader's location and the strength of opposing forces. The S-3 will then determine which subordinate unit should be tasked with the mission, say, an infantry platoon. Finally the S-3 will generate the written order to be sent to the platoon which will detail the situation, the nature of the mission, the target and the time line (pg. 56).

Planning Unit Composition

It is also the S3's responsibility to determine which unit organization configurations with yield the best result for accomplishing the mission. Battalions are composed of companies that have different functions. The companies are made up of platoons and squads. The S-3 can change the compositions of companies to suit a mission. For example, the S-3 can increase or decrease the number of platoons in an infantry rifle company. He also can attach external units temporarily to companies within the battalion. If the S3 is planning a mission where infantry ground forces are expected to encounter obstacles, she may order a detachment from a combat engineering unit to support the infantry forces. Combat engineers specialize in breaching obstacles (pg. 57, "Organization").

Coordinate with Other Staff Members

It is important that the S-3 interface not only with the S-2, but all other members of the battalion staff. Each staff member is responsible for a specific area of operations that will impact any plans the S-3 makes. If an S-3 wants to order an attack mission, the S4 (logistics) officer must be notified to ensure that enough weapons and ammunition are on hand. The Fire Support Officer must be informed so that the field artillery units know where to aim their cannon if fire support is needed. If these officers do not communicate with each other throughout the planning process, success is unlikely (pg 58).