Giovan Battista Belluzzi (1506–54) was a San Marino native who served as chief military engineer to Cosimo I de' Medici (1519–74), duke of Florence. This manuscript, believed to be in Belluzzi’s own hand, was written for Stefano IV Colonna, a Florentine general also in the employment of the Medici family. The manuscript contains instructions for building military fortifications in remote areas, using only local resources such as earth and wood as structural elements. The text includes a discourse on how to evaluate the condition of the soil, how to treat soil to turn it into a binding agent or plaster, and how to apply it to wooden supports to fashion a defensive wall. The text also includes measurements for determining the height and length of a planned wall and a description of where to position the framework section of a wall. The manuscript contains a series of drawings to illustrate the methods described in the text, including an image depicting the pattern in which wooden poles were to be placed in the ground to form a section of wall. Another image shows a platform that was to be built so that workers could construct the elevated parts of the fortification. Belluzzi also provides illustrations of tools, methods of weaving strips of wood to form parts of walls, and other ways of using local elements to build fortified structures. He concludes the work with a description of the walls of the city of Pistoia, which he constructed in 1544. Belluzzi died in Medici service during the siege of Siena.