Musket
Countermarch

As muskets became the default weapon of armies, the slow reloading time became an increasing problem. The difficulty of reloading—and thus the time needed to do it—was diminished by making the musket ball much smaller than the internal diameter of the barrel, so as the interior of the barrel became dirty from soot from previously fired rounds, the musket ball from the next shot could still be easily rammed. To keep the ball in place once the weapon was loaded, it would be partially wrapped in a small piece of cloth. However, the smaller ball could move within the barrel as the musket was fired, decreasing the accuracy of musket fire (it was complained that it took a man's weight in lead musket balls to kill him).

The development of volley fire —by the Ottomans, the Chinese, the Japanese, and the Dutch—made muskets more feasible for widespread adoption by the military. The volley fire technique transformed soldiers carrying firearms into organized firing squads with each row of soldiers firing in turn and reloading in a systematic fashion. Volley fire was implemented with cannons as early as 1388 by Ming artillerists, but volley fire with matchlocks was not implemented until 1526 when the Ottoman Janissaries used it during the Battle of Mohács. The matchlock volley fire technique was next seen in mid-16th-century China as pioneered by Qi Jiguang and in late-16th-century Japan. Qi Jiguang elaborates on his countermarch volley fire technique in the Jixiao Xinshu:

All the musketeers, when they get near the enemy are not allowed to fire early, and they're not allowed to just fire everything off in one go, whenever the enemy then approaches close, there won't be enough time to load the guns (銃裝不及), and frequently this mismanagement costs the lives of many people. Thus, whenever the enemy gets to within a hundred paces' distance, they are to wait until they hear a blast on the bamboo flute, at which they deploy themselves in front of the troops, with each platoon (哨) putting in front one team (隊). They wait until they hear their own leader fire a shot, and only then are they allowed to give fire. Each time the trumpet gives a blast, they fire one time, spread out in battle array according to the drilling patterns. If the trumpet keeps blasting without stopping, then they are allowed to fire all together until their fire is exhausted, and it's not necessary to divide into layers.

Frederick Lewis Taylor claims that a kneeling volley fire may have been employed by Prospero Colonna 's arquebusiers as early as the Battle of Bicocca (1522). However, this has been called into question by Tonio Andrade who believes this is an over interpretation as well as mis-citation of a passage by Charles Oman suggesting that the Spanish arquebusiers kneeled to reload, when in fact Oman never made such a claim. This is contested by Idan Sherer, who quotes Paolo Giovio saying that the arquebusiers kneeled to reload so that the second line of arquebusiers could fire without endangering those in front of them.

European gunners might have implemented countermarch to some extent since at least 1579 when the Englishman Thomas Digges suggested that musketeers should, "after the old Romane manner make three or four several fronts, with convenient spaces for the first to retire and unite himselfe with the second, and both these if occasion so require, with the third; the shot having their convenient lanes continually during the fight to discharge their peces." The Spanish too displayed some awareness of the volley technique. Martín de Eguiluz described it in the military manual, Milicia, Discurso y Regla Militar, dating to 1586: "Start with three files of five soldiers each, separated one from the other by fifteen paces, and they should comport themselves not with fury but with calm skillfulness such that when the first file has finished shooting they make space for the next (which is coming up to shoot) without turning face, countermarching to the left but showing the enemy only the side of their bodies, which is the narrowest of the body, and about one to three steps behind, with five or six pellets in their mouths, and two lighted matchlock fuses... and they load promptly... and return to shoot when it's their turn again." Most historians, including Geoffrey Parker, have ignored Eguiluz, and have erroneously attributed the invention of the countermarch to Maurice of Nassau, although the publication of the Milicia, Discurso y Regla Militar antedates Maurice's first letter on the subject by two years. Regardless, it is clear that the concept of volley fire had existed in Europe for quite some time during the 16th century, but it was in the Netherlands during the 1590s that the musketry volley really took off. The key to this development was William Louis, Count of Nassau-Dillenburg who in 1594 described the technique in a letter to his cousin:

I have discovered... a method of getting the musketeers and soldiers armed with arquebuses not only to keep firing very well but to do it effectively in battle order... in the following manner: as soon as the first rank has fired together, then by the drill they will march to the back. The second rank, either marching forward or standing still, fire together then march to the back. After that, the third and following ranks will do the same. Thus before the last ranks have fired, the first will have reloaded.
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