Dragon-shaped, mobile fortress equipped cannons and capable of carrying troops, with a ladder device mounted on the front used for scaling walls or as a bridge during siege warfare. Roberto Valturio, 1472. Roberto Valturio (1405-1475) was an Italian engineer and writer. He was the author of the military treatise De Re militari (1472). The work consists of a preface, with a dedication to Sigismondo Pandolfo Malatesta; a list of the classical works mentioned and an introduction on the history of warfare. The work was widely known: the French King Louis XI of France, the Hungarian king Matthias Corvinus, the Duke of Urbino Federico da Montefeltro and the ruler of Florence Lorenzo de' Medici had a copy of the printed book.