The principles of war are a concept of knowledge and teaching about warfare in a historical perspective. The use of the principles has been debated for many years. This has led to fragmentation within military theory. However, the principles of war play a central tole in Swedish doctrine and field manuals. One of the principles is concentration on force. Concentration of force means to concentrating resources in time and space to create local superiority against an opponent. This paper aims to analyse how concentration of force can be achieved. To do so the author has analysed the military theorist Carl von Clausewitz´s definition of concentration of force. By analysing Clasuewitz´s definition, the author has identified four variables with the aim of explaning how a successful concentration can be achieved: Effect, Command, Sustainability and Professionalism. To analyse the principle, these variables are tested in two cases, operation Goodwood and Cobra, how took part during World War II to whether concentration of force can explain the outcome of these operations. After the analysis, the author has concluded that concentration of force can explain the outcome of the cases, but only as a contributing factor.