This article aims to reconstruct the defensive organization of the Florentine Republic, according to the information contained in the citizen statutes of 1415. The analysis will focus on management of the fortifications, carry out by numerous offices established by city government for the defense of the borders and the protection of the conquered territories. The results will outline a complex organization, structured on several levels of control and will show the considerable number of officers and soldiers, as well as the remarkable economic resources necessary to make this system work properly.