Amidst the main camps of the “Camp de Boulogne”, the one from Montreuil-sur-Mer gathered the three divisions of the left corps commanded by Marshal Ney; in total, eleven infantry regiments. The extent of these camps is surprising, as well as their elongated shape and their regularity. A precise principle rules their organisation: the order of battle. Thus, in observing the cavities left by these camps, it is the infantry on the battlefield – “the soul of the army” said Napoléon – that we observe. In detail, these camps are complex and only the cross examination of the sources can help refine its comprehension. The fine analysis of the organisation rules allows a better understanding of the soldier’s condition, which is the other stake of these researches. Trying to grasp the condition of the soldier, during the battle or waiting for it, involves understanding the context from which it stems, the battlefield or the camp. What is a camp? What is this “Camp de Boulogne”? These are two questions this dissertation intends to answer. This cross-questioning necessarily implies a reflection on the military organisation and the campaigns preceding the development of the Camp de Boulogne. Capturing the camp, as a system and in its operation, to capture the men occupying it, young conscripts or veterans of the wars of the French Revolution, those are the two main objectives of this work. The soldier and the camp, such are the two lines of force which dominate the dissertation. We also raise the question of the real efficiency of this camp on the preparation of the victorious troops.