Few technological innovations have been as momentous as the development of gunpowder. Gunpowder was the first major harnessing of chemical energy by humans since the mastery of fire, and the development of gunpowder artillery has been commonly used since the eighteenth century as the original and archetypical example of a “military revolution.” Whether cannon actually did “revolutionize” warfare is a debated subject, but most of those who argue that it did do so date the Artillery Revolution to some time in the first half of the fifteenth century. By then, however, gunpowder artillery had been in use for around a century. Our sources allow us a reasonably good understanding of the development of guns during the fifteenth century, but our information about the fourteenth century (especially in the first fifty years, from c.1326 to c.1375) is relatively thin.

The same is true of the development of gunpowder. All gunpowder includes a mix of saltpeter, sulfur, and charcoal. Nineteenth-century gunpowder was typically mixed with ratios of around 75:10:15 (in that order), i.e. with a saltpeter:sulfur ratio of 7.5:1 and a saltpeter content of 75%. Several early fifteenth-century recipes come fairly close to that mix, though some have significantly more sulfur content. A recipe from Montauban of the turn of the fifteenth century calls for 22:4:5 (71%/13%/16%). One of the two Frankfurter Büchsenmeisterblätter recipes (c.1400) gives a ratio 5:1:1 (71%/14%/14%). The 1405 manuscript of Bellifortis includes a 4:1:0.5 (73%/18%/9%) mix; the Büchsenmeisterbuch (composed at an uncertain date before 1411, probably around 1400) recommends the same mixture with small additions of salarmoniac (ammonium chloride) and salpracticum (a mix of saltpeter and salarmoniac), or 3.5:1:0.5 (70%/20%/10%) without those extra ingredients. Abundant evidence shows a shift towards – or back towards – somewhat lower saltpeter content in later fifteenth-century recipes, including those edited by Trevor Russell Smith in the following article in this volume of the Journal of Medieval Military History.