Recto: "Libro Primo, Chapo Quarto..." (Vitruvius, Book 1, Chapter 4); Verso: The Fortification of City Walls (Vitruvius, Book 1, Chapter 5).

The creator of this drawing was an experienced draftsman of military technology and architecture, as is evident by his use of perspective and in the level of surface detail with which he elaborated the forms presented here. This proficiency is clear when compared to illustrations of military fortifications in early printed editions of Vitruvius (see the edition of 1524 by Durantino).The fortification of cities and ports was a specialty of the Sangallo family and of Antonio da Sangallo "The Younger" in particular, as he worked as a military engineer in the papal court in Rome. A prolific architect and draftsman, Antonio "The Younger" owned, among others, a pocket-sized, printed Latin edition of Vitruvius, which he annotated with drawings and text. It is today part of the Metropolitan Museum's vast collection of early Vitruvius editions. His younger brother and much-overshadowed amanuensis for many of his military drawings, Giovanni Battista da Sangallo "Il Gobbo," left an insightful book of commentary on Vitruvius, which, according to a 1568 biography by Giorgio Vasari, "never saw the light of publication."

A recent discovery, this sheet and seven others (acc. nos. 2008.105.1-8) comprised a manuscript draft for an Italian edition of the sole surviving architectural treatise of Roman antiquity, Ten Books on Architecture by Marcus Pollius Vitruvius (late first century B.C.). Had the project been completed, it would have ranked among the brilliantly imaginative works of Renaissance interpretive architectural theory. The drawings also exhibit a beautifully expressive handling of the pen. Comparisons of style as well as of the shorthand notation in the sketching of human figures suggest a close kinship with drawings by Bastiano "Aristotile" da Sangallo (Florence, 1481 – Florence 1551) and the collaborators that helped him draw and write the motifs of marginalia in a printed 1486 edition of Vitruvius (Biblioteca Corsiniana, Accademia Nazionale dei Lincei, Rome) that was reworked in the 1530s. By all accounts a virtuoso stage set designer, Bastiano da Sangallo-the cousin and closest collaborator of Antonio da Sangallo "The Younger" and Giovanni Battista da Sangallo "Il Gobbo"-was Michelangelo's assistant in the Sistine Chapel and took the surname of "Aristotile" for his love of antiquity. Members of the Sangallo family had been deeply interested in Vitruvius for at least two generations.