The fifteenth century in European history is traditionally seen as marking the end of medieval times and the dawn of a new age, “the renaissance”. The “the” is important, because other “renaissances”, such as that dubbed Carolingian and that ascribed to the twelfth century, are distinguished by a temporal qualifier not apparently needed by their later incarnation. The significance of the last of the renaissances, however, is that it was accompanied by the significant changes in economy and society that truly mark out new times. The scientific and artistic progress recorded in each renaissance was based on recovering the lost secrets of the ancients, and fifteenth-century humanists were no less anxious than Charlemagne that their work should be understood in this light, not as a revolution that marked the beginning of a new age. This is ironic in light of the massive transformation getting underway during these decades. By the sixteenth century, world-changing events included the first overseas expansion of Christian states, led by Portugal (which had started early in the fifteenth century) and then by newly unified Spain, leading to the extortion of vast wealth from the Americas at the cost of the virtual annihilation of the native populations. While the “universal” authority of the Church now reached new continents, in Europe it was forever overturned by the protestant reformation, which was also deployed as cover by many rulers to reinforce their efforts to establish independent states. The biggest changes simultaneously occurred in society and the economy, where feudal social structures gave way to the progressive enrichment of traders, merchants and manufacturers and the continuing development of capitalism. This new class was achieving a weight in society that would in due course assert a political voice. Gutenberg’s invention of the printing press brought mass production of reading material to Europe from the middle of the fifteenth century with growing social impact. Some of the military engineering texts discussed here were among that material. Countries that did not develop this way (even if printing was already available, as in China) would be overtaken in economic, scientific and technological progress by Europe for the first time, Ming China being a classic example once the dynasty resolved to close itself off from the outside world in mid-century.