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Early modern period

By the 16th century, cannons were made in a great variety of lengths and bore diameters, but the general rule was that the longer the barrel, the longer the range. Some cannons made during this time had barrels exceeding 10 ft (3.0 m) in length, and could weigh up to 20,000 pounds (9,100 kg). Consequently, large amounts of gunpowder were needed to allow them to fire stone balls several hundred yards. By mid-century, European monarchs began to classify cannons to reduce the confusion. Henry II of France opted for six sizes of cannon, but others settled for more; the Spanish used twelve sizes, and the English sixteen. They are, from largest to smallest: the cannon royal, cannon, cannon serpentine, bastard cannon, demicannon, pedrero, culverin, basilisk, demiculverin, bastard culverin, saker, minion, falcon, falconet, serpentine, and rabinet. Better powder had been developed by this time as well. Instead of the finely ground powder used by the first bombards, powder was replaced by a "corned" variety of coarse grains. This coarse powder had pockets of air between grains, allowing fire to travel through and ignite the entire charge quickly and uniformly.

The end of the Middle Ages saw the construction of larger, more powerful cannon, as well as their spread throughout the world. As they were not effective at breaching the newer fortifications resulting from the development of cannon, siege engines —such as siege towers and trebuchets —became less widely used. However, wooden "battery-towers" took on a similar role as siege towers in the gunpowder age—such as that used at Siege of Kazan in 1552, which could hold ten large-calibre cannon, in addition to 50 lighter pieces. Another notable effect of cannon on warfare during this period was the change in conventional fortifications. Niccolò Machiavelli wrote, "There is no wall, whatever its thickness that artillery will not destroy in only a few days." Although castles were not immediately made obsolete by cannon, their use and importance on the battlefield rapidly declined. Instead of majestic towers and merlons, the walls of new fortresses were thick, angled, and sloped, while towers became low and stout; increasing use was also made of earth and brick in breastworks and redoubts. These new defences became known as bastion forts, after their characteristic shape which attempted to force any advance towards it directly into the firing line of the guns. A few of these featured cannon batteries, such as the House of Tudor 's Device Forts in England. Bastion forts soon replaced castles in Europe and, eventually, those in the Americas as well.

By the end of the 15th century, several technological advancements made cannons more mobile. Wheeled gun carriages and trunnions became common, and the invention of the limber further facilitated transportation. As a result, field artillery became more viable, and began to see more widespread use, often alongside the larger cannons intended for sieges. Better gunpowder, cast-iron projectiles (replacing stone), and the standardisation of calibres meant that even relatively light cannons could be deadly. In The Art of War, Niccolò Machiavelli observed that "It is true that the arquebuses and the small artillery do much more harm than the heavy artillery." This was the case at the Battle of Flodden, in 1513: the English field guns outfired the Scottish siege artillery, firing two or three times as many rounds. Despite the increased maneuverability, however, cannon were still the slowest component of the army: a heavy English cannon required 23 horses to transport, while a culverin needed nine. Even with this many animals pulling, they still moved at a walking pace. Due to their relatively slow speed, and lack of organisation, and undeveloped tactics, the combination of pike and shot still dominated the battlefields of Europe.

Innovations continued, notably the German invention of the mortar, a thick-walled, short-barrelled gun that blasted shot upward at a steep angle. Mortars were useful for sieges, as they could hit targets behind walls or other defences. This cannon found more use with the Dutch, who learnt to shoot bombs filled with powder from them. Setting the bomb fuse was a problem. "Single firing" was first used to ignite the fuse, where the bomb was placed with the fuse down against the cannon's propellant. This often resulted in the fuse being blown into the bomb, causing it to blow up as it left the mortar. Because of this, "double firing" was tried where the gunner lit the fuse and then the touch hole. This required considerable skill and timing, and was especially dangerous if the gun misfired, leaving a lighted bomb in the barrel. Not until 1650 was it accidentally discovered that double-lighting was superfluous as the heat of firing would light the fuse.

Gustavus Adolphus of Sweden emphasised the use of light cannon and mobility in his army, and created new formations and tactics that revolutionised artillery. He discontinued using all 12 pounder—or heavier—cannon as field artillery, preferring, instead, to use cannons that could be handled by only a few men. One obsolete type of gun, the " leatheren ", was replaced by 4 pounder and 9 pounder demi-culverins. These could be operated by three men, and pulled by only two horses. Gustavus Adolphus's army was also the first to use a cartridge that contained both powder and shot which sped up reloading, increasing the rate of fire. Finally, against infantry he pioneered the use of canister shot —essentially a tin can filled with musket balls. Until then there was no more than one cannon for every thousand infantrymen on the battlefield but Gustavus Adolphus increased the number of cannons sixfold. Each regiment was assigned two pieces, though he often arranged them into batteries instead of distributing them piecemeal. He used these batteries to break his opponent's infantry line, while his cavalry would outflank their heavy guns.

At the Battle of Breitenfeld, in 1631, Adolphus proved the effectiveness of the changes made to his army, by defeating Johann Tserclaes, Count of Tilly. Although severely outnumbered, the Swedes were able to fire between three and five times as many volleys of artillery, and their infantry's linear formations helped ensure they did not lose any ground. Battered by cannon fire, and low on morale, Tilly's men broke ranks and fled.

In England, cannons were being used to besiege various fortified buildings during the English Civil War. Nathaniel Nye is recorded as testing a Birmingham cannon in 1643 and experimenting with a saker in 1645. From 1645 he was the master gunner to the Parliamentarian garrison at Evesham and in 1646 he successfully directed the artillery at the Siege of Worcester, detailing his experiences and in his 1647 book The Art of Gunnery. Believing that war was as much a science as an art, his explanations focused on triangulation, arithmetic, theoretical mathematics, and cartography as well as practical considerations such as the ideal specification for gunpowder or slow matches. His book acknowledged mathematicians such as Robert Recorde and Marcus Jordanus as well as earlier military writers on artillery such as Niccolò Fontana Tartaglia and Thomas (or Francis) Malthus (author of A Treatise on Artificial Fire-Works).

Around this time also came the idea of aiming the cannon to hit a target. Gunners controlled the range of their cannons by measuring the angle of elevation, using a "gunner's quadrant". Cannons did not have sights; therefore, even with measuring tools, aiming was still largely guesswork.

In the latter half of the 17th century, the French engineer Sébastien Le Prestre de Vauban introduced a more systematic and scientific approach to attacking gunpowder fortresses, in a time when many field commanders "were notorious dunces in siegecraft". Careful sapping forward, supported by enfilading ricochets, was a key feature of this system, and it even allowed Vauban to calculate the length of time a siege would take. He was also a prolific builder of bastion forts, and did much to popularize the idea of "depth in defence" in the face of cannon. These principles were followed into the mid-19th century, when changes in armaments necessitated greater depth defence than Vauban had provided for. It was only in the years prior to World War I that new works began to break radically away from his designs.