Medieval warfare
Viking longships were swift and easily manoeuvered; they could navigate deep seas or shallow rivers, and could carry warriors that could be rapidly deployed directly onto land due to the longships being able to land directly. The longship was the enabler of the Viking style of warfare that was fast and mobile, relying heavily on the element of surprise. The usual method was to approach a target with the element of surprise and then retire swiftly using guerrilla-style fighting. The fully armoured Viking raider would wear an iron helmet and a mail hauberk, and fight with a combination of axe, sword, shield, spear or great "Danish" two-handed axe, although the typical raider would be unarmoured, carrying only a bow and arrows, a seax, a shield and spear. European countries with a weak system of government would be unable to organize a suitable response and would naturally suffer the most to Viking raiders. Viking raiders always had the option to fall back in the face of a superior force or stubborn defence and then reappear to attack other locations or retreat to their bases. As time went on, Viking raids became more sophisticated, with coordinated strikes involving multiple forces and large armies, as the "Great Heathen Army" that ravaged Anglo-Saxon England in the 9th century. In time, the Vikings began to hold on to the areas they raided, first wintering and then consolidating footholds for further expansion later.
After the Vikings consolidated their kingdoms of Denmark, Norway, and Sweden, this period marks the end of significant raider activity both for plunder or conquest; adapting a more continental European tradition of warfare, whilst retaining an emphasis on naval power – the "Viking" clinker-built warship was used in the war until the 14th century. However, developments in shipbuilding elsewhere removed the advantage they previously enjoyed at sea, whilst castle building throughout frustrated and eventually ended Viking raids.
The Scandinavian armies of the High Middle Ages followed the usual pattern of the Northern European armies, but with a stronger emphasis on infantry. The terrain of Scandinavia favoured heavy infantry, and whilst the nobles fought mounted in the continental fashion, the Scandinavian peasants formed a well-armed and well-armoured infantry, of which approximately 30% to 50% would be archers or crossbowmen. The crossbow, the flatbow and the longbow were especially popular in Sweden and Finland. The chainmail, the lamellar armour and the coat of plates were the usual Scandinavian infantry armour before the era of plate armour.

Mongols: By 1241, having conquered large parts of Russia, the Mongols continued the invasion of Europe with a massive three-pronged advance, following the fleeing Cumans, who had established an uncertain alliance with King Bela IV of Hungary. They first invaded Poland, and finally, Hungary, culminating in the crushing defeat of the Hungarians in the Battle of Mohi. The Mongol aim seems to have consistently been to defeat the Hungarian-Cuman alliance. The Mongols raided across the borders to Austria and Bohemia in the summer when the Great Khan died, and the Mongol princes returned home to elect a new Great Khan.
The Golden Horde would frequently clash with Hungarians, Lithuanians and Poles in the thirteenth century, with two large raids in the 1260s and 1280s respectively. In 1284 the Hungarians repelled the last major raid into Hungary, and in 1287 the Poles repelled a raid against them. The instability in the Golden Horde seems to have quieted the western front of the Horde. Also, the large scale invasions and raiding that had previously characterized the expansion of the Mongols was cut short probably in some part due to the death of the last great Mongol leader, Tamerlane.
The Hungarians and Poles had responded to the mobile threat by extensive fortification-building, army reform in the form of better-armoured cavalry, and refusing battle unless they could control the site of the battlefield to deny the Mongols local superiority. The Lithuanians relied on their forested homelands for defence and used their cavalry for raiding into Mongol-dominated Russia. When attacking fortresses they would launch dead or diseased animals into fortresses to help spread disease.

Turks and Central Asia: An early Turkic group, the Seljuks, were known for their cavalry archers. These fierce nomads were often raiding empires, such as the Byzantine Empire, and they scored several victories using mobility and timing to defeat the heavy cataphracts of the Byzantines.
One notable victory was at Manzikert, where conflict among the generals of the Byzantines gave the Turks the perfect opportunity to strike. They hit the cataphracts with arrows, and outmanoeuvred them, then rode down their less mobile infantry with light cavalry that used scimitars (in use since the 9th century). When gunpowder was introduced, the Ottoman Turks of the Ottoman Empire hired the mercenaries that used the gunpowder weapons and obtained their instruction for the Janissaries. Out of these Ottoman soldiers rose the Janissaries (yeni ceri; "new soldier"), from which they also recruited many of their heavy infantry. Along with the use of cavalry and early grenades, the Ottomans mounted an offensive in the early Renaissance period and attacked Europe, taking Constantinople by massed infantry assaults.
Like many other nomadic peoples, the Turks featured a core of heavy cavalry from the upper classes. These evolved into the Sipahis (feudal landholders similar to western knights and Byzantine pronoiai) and Qapukulu (door slaves, taken from youth like Janissaries and trained to be royal servants and elite soldiers, mainly cataphracts).
Already by the late 13th century, the Khilji dynasty utilized several siege technologies such as trebuchets, ballistas and wooden parapets by their war engineers. In order to breach a fortification's curtain walls, long earthen-ramps were used to fill up moats. In ranged military techniques, they used the powerful war-horses from Central Asia with mounted archers.

Equipment: Weapons
Medieval weapons consisted of many different types of ranged and hand-held objects:

Melee
Battleaxe
Horseman's pick
Blades
Arming sword
Dagger
Knife
Longsword
Messer
Blunt weapons
Club
Mace
War hammer
Polearm
Halberd
Lance
Military fork, the weaponized Pitchfork
Pollaxe
Spear
Ranged
Bow
Longbow
Crossbow
Throwing axe
Throwing spear and Javelin
Sling
Armour

Body armour
Leather
Fabric
Chain mail
Brigandine
Plate
Shield
Helmet
Artillery and Siege engine

Battering ram
Catapult
Trebuchet
Ballista
Siege tower
Animals

Camels in warfare
Dogs in warfare
Horses in warfare and Horses in the Middle Ages
War elephant
War pigs

See also: 

Notes: 

References: Archdeacon, Thomas of Split (2006). History of the Bishops of Salona and Split – Historia Salonitanorum atque Spalatinorum pontificum (in Latin and English). Budapest: Central European University Press. ISBN 978-963-7326-59-2.
DeVries, Kelly (1992), Military Medieval Technology, Broadview Press, ISBN 0-921149-74-3
Fernández-Armesto, Felipe (1999), "Naval Warfare after the Viking Age, c. 1100–1500", in Keen, Maurice (ed.), Medieval Warfare: A History, Oxford: Oxford University Press, pp. 230–252, ISBN 0-19-820639-9
Gillingham, John (1992), "William the Bastard at War", in Strickland, Matthew (ed.), Anglo-Norman warfare: Studies in Late Anglo-Saxon and Anglo-Norman Military Organization and Warfare, Woodbridge: The Boydell Press, pp. 143–160, ISBN 0-85115-327-5
Glete, Jan, Warfare at Sea, 1500–1650: Maritime Conflicts and the Transformation of Europe. Routledge, London. 2000. ISBN 0-415-21455-6
Goffart, Walter (1977), "The date and purpose of Vegetius' De Re Militari", Traditio, xxxiii: 65–100, doi:10.1017/S0362152900009077, JSTOR 27831025, S2CID 151406462
Guilmartin, John Francis, Gunpowder and Galleys: Changing Technology and Mediterranean Warfare at Sea in the Sixteenth Century. Cambridge University Press, London. 1974.
Hattendorf, John B. & Unger, Richard W. (editors), War at Sea in the Middle Ages and the Renaissance. Woodbridge, Suffolk. 2003. ISBN 0-85115-903-6 [1]
Liddiard, Robert (2005), Castles in Context: Power, Symbolism and Landscape, 1066 to 1500, Macclesfield: Windgather Press Ltd, ISBN 0-9545575-2-2
Lehmann, L. Th., Galleys in the Netherlands. Meulenhoff, Amsterdam. 1984.