Medieval warfare
The carro della guerra of Milan was described in detail in 1288 by Bonvesin de la Riva in his book on the "Marvels of Milan". Wrapped in scarlet cloth and drawn by three yoke of oxen that were caparisoned in white with the red cross of Saint Ambrose, the city's patron, it carried a crucifix so massive it took four men to step it in place, like a ship's mast.

Naval warfare: The waters surrounding Europe can be grouped into two types which affected the design of craft that traveled and therefore the warfare. The Mediterranean and Black Seas were free of large tides, generally calm, and had predictable weather. The seas around the north and west of Europe experienced stronger and less predictable weather. The weather gauge, the advantage of having a following wind, was an important factor in naval battles, particularly to the attackers. Typically westerlies (winds blowing from west to east) dominated Europe, giving naval powers to the west an advantage. Medieval sources on the conduct of medieval naval warfare are less common than those about land-based war. Most medieval chroniclers had no experience of life on the sea and generally were not well informed. Maritime archaeology has helped provide information.

Early in the medieval period, ships in the context of warfare were used primarily for transporting troops. In the Mediterranean, naval warfare in the Middle Ages was similar to that under late Roman Empire: fleets of galleys would exchange missile fire and then try to board bow first to allow marines to fight on deck. This mode of naval warfare remained the same into the early modern period, as, for example, at the Battle of Lepanto. Famous admirals included Roger of Lauria, Andrea Doria and Hayreddin Barbarossa.
Late medieval maritime warfare was divided in two distinct regions. In the Mediterranean, galleys were used for raiding along coasts, and in the constant fighting for naval bases. In the Atlantic and Baltic there was greater focus on sailing ships that were used mostly for troop transport, with galleys providing fighting support. Galleys were still widely used in the north and were the most numerous warships used by Mediterranean powers with interests in the north, especially the French and Iberian kingdoms.
Bulkier ships were developed which were primarily sail-driven, although the long lowboard Viking-style rowed longship saw use well into the 15th century. Their main purpose in the north remained the transportation of soldiers to fight on the decks of the opposing ship (as, for example, at the Battle of Svolder or the Battle of Sluys).
Late medieval sailing warships resembled floating fortresses, with towers in the bows and at the stern (respectively, the forecastle and aftcastle).  The large superstructure made these warships quite unstable, but the decisive defeats that the more mobile but considerably lower boarded longships suffered at the hands of high-boarded cogs in the 15th century ended the issue of which ship type would dominate northern European warfare.

Introduction of guns: The introduction of guns was the first step towards major changes in naval warfare, but it only slowly changed the dynamics of ship-to-ship combat. The first guns on ships were introduced in the 14th century and consisted of small wrought-iron pieces placed on the open decks and in the fighting tops, often requiring only one or two men to handle them. They were designed to injure, kill or simply stun, shock and frighten the enemy before boarding.

As guns were made more durable to withstand stronger gunpowder charges, they increased their potential to inflict critical damage to the vessel rather than just their crews. Since these guns were much heavier than the earlier anti-personnel weapons, they had to be placed lower in the ships, and fire from gunports, to avoid ships becoming unstable. In Northern Europe the technique of building ships with clinker planking made it difficult to cut ports in the hull; clinker-built (or clench-built) ships had much of their structural strength in the outer hull. The solution was the gradual adoption of carvel-built ships that relied on an internal skeleton structure to bear the weight of the ship.
The first ships to actually mount heavy cannon capable of sinking ships were galleys, with large wrought-iron pieces mounted directly on the timbers in the bow. The first example is known from a woodcut of a Venetian galley from 1486. Heavy artillery on galleys was mounted in the bow which fit conveniently with the long-standing tactical tradition of attacking head-on and bow-first. The ordnance on galleys was quite heavy from its introduction in the 1480s, and capable of quickly demolishing medieval-style stone walls that still prevailed until the 16th century.
This temporarily upended the strength of older seaside fortresses, which had to be rebuilt to cope with gunpowder weapons. The addition of guns also improved the amphibious abilities of galleys as they could assault supported with heavy firepower, and could be even more effectively defended when beached stern-first. Galleys and similar oared vessels remained uncontested as the most effective gun-armed warships in theory until the 1560s, and in practice for a few decades more, and were considered a grave risk to sailing warships.

Rise of infantry: In the Medieval period, the mounted cavalry long held sway on the battlefield. Heavily armoured mounted knights represented a formidable foe for reluctant peasant draftees and lightly armoured freemen. To defeat mounted cavalry, infantry used swarms of missiles or a tightly packed phalanx of men, techniques honed in antiquity by the Greeks.

Swiss pikemen: The use of long pikes and densely packed foot troops was not uncommon in the Middle Ages. The Flemish footmen at the Battle of the Golden Spurs met and overcame French knights in 1302, as the Lombards did in Legnano in 1176 and the Scots held their own against heavily armoured English cavalry. During the St. Louis crusade, dismounted French knights formed a tight lance-and-shield phalanx to repel Egyptian cavalry.  The Swiss used pike tactics in the late medieval period. While pikemen usually grouped and awaited a mounted attack, the Swiss developed flexible formations and aggressive manoeuvring, forcing their opponents to respond. The Swiss won at Morgarten, Laupen, Sempach, Grandson and Murten, and between 1450 and 1550 every leading prince in Europe (except the English and Scottish) hired Swiss pikemen, or emulated their tactics and weapons (e.g., the German Landsknechte).

Welsh and English longbowmen: The Welsh and English longbowmen used a single-piece longbow (but some bows later developed a composite design) to deliver arrows that could penetrate contemporary mail and damage/dent plate armour. The longbow was a difficult weapon to master, requiring long years of use and constant practice. A skilled longbowman could shoot about 12 shots per minute.  This rate of fire was far superior to competing weapons like the crossbow or early gunpowder weapons. The nearest competitor to the longbow was the much more expensive crossbow, used often by urban militias and mercenary forces. The crossbow had greater penetrating power and did not require the extended years of training. However, it lacked the rate of fire of the longbow.
At Crécy and Agincourt bowmen unleashed clouds of arrows into the ranks of knights. At Crécy, even 5,000 Genoese crossbowmen could not dislodge them from their hill. At Agincourt, thousands of French knights were brought down by armour-piercing bodkin point arrows and horse-maiming broadheads. Longbowmen decimated an entire generation of the French nobility.

Transition to gunpowder warfare: In 1326 the earliest known European picture of a gun appeared in a manuscript by Walter de Milemete. In 1350, Petrarch wrote that the presence of cannons on the battlefield was 'as common and familiar as other kinds of arms'.
Early artillery played a limited role in the Hundred Years' War, and it became indispensable in the Italian Wars of 1494–1559, marking the beginning of early modern warfare. Charles VIII, during his invasion of Italy, brought with him the first truly mobile siege train: culverins and bombards mounted on wheeled carriages, which could be deployed against an enemy stronghold immediately after arrival.

Strategy and tactics: Medieval campaigns were planned with strategy in mind, such as maintaining unity in morale, planning troop movements, and mount offensives with numerical advantages. Medieval armies used strategic deception, such as misleading troop movements, to take opposing armies by surprise. They would also spread misinformation regarding army size and provisions.
One common tactic used in medieval warfare was raiding; this benefitted the attacking army by with new supplies and wealth while damaging the target's resources.

De re militari: Publius Flavius Vegetius Renatus wrote De re militari (Concerning Military Matters) possibly in the late 4th century. Described by historian Walter Goffart as "the bible of warfare throughout the Middle Ages", De re militari was widely distributed through the Latin West. While Western Europe relied on a single text for the basis of its military knowledge, the Byzantine Empire in Southeastern Europe had a succession of military writers.