It is well known that the level of knowledge and experience characterize a technician’s performance and his art is supported by various sciences. In accordance to this, the militaries today being professionals must have complete and specialized knowledge, coupled with expertise, dedicated knowledge which would ensure effective action and fulfillment of any given mission, with minimal costs in human and material. In parallel, the military sciences must not only follow the latest technological developments, but ought to evolve and adapt the scientific knowledge to the needs of military technology, to analyze the current and emerging threats, to supply with the appropriate knowhow, dedicated technique and methodology that is directly or indirectly involved staff in military operations. Following to the above reasoning, the aim of this presentation is to highlight the need of forced coexistence of knowledge and expertise with experience to the current members of Armed Forces. However it is briefly represented, in the form of mathematical equations and with simple operational examples, the chain of relationship among the involved forces and the outcome of the battle in a modern military operation. It is specifically noted, in all three phases of a military operation, (planning, preparation, execution), the determining factors of the participants’ professionalism and the means’ quality-technology, (friendly –opponent), which are combined with the extensive knowledge and experience of the opponents, determining the respective plan of action, applied tactics, and involvement in general operational needs. It is also underlined the importance of those key factors of mission success, affecting efficiency and the cost elements, particularly critical for Greece today. The cost – effectiveness is a function of the applied military action, the particular expertise of the planner – executor and effectiveness of the involved forces and means, (tactic, weaponry, technique, timing, power of strike) and especially the used force multipliers. Undoubtedly the operational effect will be proportional to the product of the applied quantitative and qualitative force in a given time and a natural consequence of the quality performance of the involved armed forces and the technology used.