Geometry as a tool for the design of military architecture: the experience of Giovanni Battista Antonelli

The design of defensive fortresses during the sixteenth century was completed by means of drawing and geometry, by fixing the plan of the pentagonal bastions starting from the line of cannons enfilading fire and their fifle range. The proportions of the project derived mainly from ballistics studies and geometry was considered to be the essential tool every technician should use to draw up an efficient protection. Giovanni Battista Antonelli, a military engineer of Italian descent and the first member of his important family that worked for the Spanish kingdom for almost a century, explains in his treatise the compositional logics and the necessary proportions used for the design of defensive buildings. His theoretical work on modern fortifications, entitled Epitomi delle fortificationi moderne di Giovambatta Antonelli, never published and written in Spain between 1560 and 1561, elucidates the geometric rules to project the elements a modern fortification is composed of. These elements, e.g. ramparts, curtains, moat, embrasures and so on, are described in detail in the first book of the Epitomi, specifically dedicated to the defensive architecture, that also gives some information about the different metric units of measurements for the correct dimensioning of architecture, relating the measure in foot units of each country, both in Italy and in Spain. The iconographic setting that enriches the text of the ancient manuscript presents some schematic images that have been examined as well as shaped in a virtual three-dimensional model, in order to provide an exact reconstruction of the "royal bastion" as suggested by Antonelli. The research aims at highlighting the importance of the activities in defensive architecture by Antonelli, and the heritage passed on his family, who disseminated the sixteenth-century architecture in the whole wide world, from Italy to Europe and even to the Caribbean.