This monograph discusses the advantage of using a functional approach to planning. The January 1997 Coordinating Draft of FM 100-5 Operations introduces core functions to the fundamentals of Army operations. Core functions are the fundamental actions of a military force. The monograph first describes the proposed core functions. Following this description, relevant writings of military theorists are reviewed along with approved doctrine. Current doctrine prescribes a system rather than functional method of planning. The core functions and the Battlefield Operating Systems (BOS)/Operational Operating Systems (OOS) are analyzed to determine their utility in planning. They are then compared to determine which best supports commanders and planners as they design operations to achieve assigned objectives. The monograph concludes that the core functions are useful to Army planners. They provide a simple and holistic guide to the development of creative operational concepts. The core functions are more adaptable to the broad range of army units and missions than the operating systems. They grow with the leader and evolve with the military force.