Combined arms
Ancient warfare: Combined arms operations date back to antiquity, where armies would usually field a screen of skirmishers to protect their spearmen during the approach to contact. Especially in the case of the Greek hoplites, however, the focus of military thinking lay almost exclusively on the heavy infantry. In more elaborate situations armies of various nationalities fielded different combinations of light, medium, or heavy infantry, cavalry, chariotry, camelry, elephantry, and artillery (mechanical weapons). Combined arms in this context was how to best use the cooperating units, variously armed with side-arms, spears, or missile weapons in order to coordinate an attack to disrupt and then destroy the enemy.
Philip II of Macedon greatly improved upon the limited combined arms tactics of the Greek city-states and combined the newly created Macedonian phalanx with heavy cavalry and other forces. The phalanx would hold the opposing line in place, until the heavy cavalry could smash and break the enemy line by achieving local superiority.
The early Republic Roman Legion was a combined arms force and consisted of five classes of troops. Lightly equipped velites acted as skirmishers armed with light javelins. The hastati and principes formed the main attacking strength of the legion with swords and pila, whilst the triarii formed the defensive backbone of the legion fighting as spearmen (initially as a denser Greek phalanx and later as a looser spear wall formation) with long spears and large shields. The fifth class of troops were the equites (the cavalry), which were used for scouting, pursuit and to guard the flanks.
The Legion then became notionally a unit of heavy infantrymen armed with just sword and pilum, and fielded with a small attached auxiliary skirmishers and missile troops, and incorporated a small cavalry unit. The legion was sometimes also incorporated into a higher-echelon combined arms unit – e.g., in one period it was customary for a general to command two legions plus two similarly sized units of auxiliaries, lighter units useful as screens or for combat in rough terrain. Later during the Roman Empire, auxiliary soldiers outnumbered the core legionary troops.
The army of the Han dynasty is also an example, fielding mêlée infantry (equipped with a variety of different weapons ranging from swords to pikes to halberd-like weapons), archers, crossbowmen, and cavalry (ranging from horse archers to heavy lancers). One recorded tactical formation during the Han dynasty included three ranks of halberds, swordsmen, and spearmen, supported by crossbows, and with cavalry on the flanks.
Civilizations such as the Carthaginians and Sassanids also were known to have fielded a combination of infantry supported by powerful cavalry.

Middle Ages: At the Battle of Hastings (1066) English infantry fighting from behind a shield wall were defeated by a Norman army consisting of archers, foot soldiers (infantry), and mounted knights (cavalry). One of the tactics used by the Normans was to tempt the English to leave the shield wall to attack retreating Norman infantry only to destroy them in the open with cavalry. Likewise Scottish sheltrons – which had been developed to counter the charges by English heavy cavalry, and had been used successfully against English cavalry at the Battle of Stirling Bridge (1297) – were destroyed at the Battle of Falkirk (1298) by English archers acting in concert with mounted knights. Both Hastings and Falkirk showed how combined arms could be used to defeat enemies relying on only one arm.
The English victories of Crécy, Poitiers and Agincourt were examples of a simple form of combined arms, with a combination of dismounted knights forming a foundation for formations of English longbowmen. The lightly protected longbowmen could down their French opponents at a distance, whilst the armoured men-at-arms could deal with any Frenchmen who made it to the English lines. This is the crux of combined arms: to allow a combination of forces to achieve what would be impossible for its constituent elements to do alone.
During the Middle Ages military forces used combined arms as a method of winning battles and furthering a war leader or king's long-term goals. Some historians claim that during the Middle Ages there was no strategic or tactical art to military combat. Kelly DeVries uses the Merriam-Webster definition of combat "as a general military engagement". In the pursuit of a leader's goals and self-interest tactical and strategic thinking was used along with taking advantage of the terrain and weather in choosing when and where to give battle. The simplest example is the combination of different specialties such as archers, infantry, cavalry (knights or shock mounted troops), and even peasant militia. At times, each force fought on its own and won or lost depending on the opposing military competence. During the Middle Ages leaders utilized a combination of these skilled and unskilled forces to win battles. An army that has multiple skills available can engage a larger force that incorporates mainly one or two types of troops.
Each type of military formation – infantry, archers, cavalry, or peasants – has certain advantages that the other does not have. Infantry allows a force to hold ground and in the event of overwhelming enemy forces withdraw into terrain that mounted troops cannot maneuver as easily, thus negating the advantage of the horse. Archers provide standoff with their bows or crossbows. Cavalry can maneuver faster and provide fast attack before the enemy has had time to prepare defenses. Peasants are more numerous and cheaper on the royal coffers. Over the long term the army can cross-train and learn the skills of the specialties to increase combat effectiveness. This is known as a combat multiplier today. The combination of the different skills help provide a commander the flexibility to minimize risk when it comes to engagements. The overall objective of any military force is to fight and win, while also preserving the largest number of combatants to carry on the larger strategic aims of the king. This can be seen in some of the engagements during the Middle Ages.

Examples of middle ages combined arms use in battle: The effective use of combined arms can – in conjunction with strategic and tactical considerations – overwhelm opposing forces, even those which are numerically superior. The use of terrain and weather can also aid in the use of combined arms to bring about the desired results of the commander of a military force.

Crecy-en-Ponthieu
Mid-1346, at the battle of Crecy-en-Ponthieu, an English army numbering between 3,000 and 20,000 mixed troops set up a defensive line for the oncoming French forces numbering nearly 100,000 mixed troops. The English being in a defensive position dismounted their knights to augment the infantry forces on the lines of defense. The location of the English archers is unclear from the sources – either on the flanks, intermingled with the line troops, or behind the lines. But in the most likely scenario, they were formed up along the flanks according to prior positions in previous battles. The French arrived on the battlefield and sent their crossbowmen in advance of the cavalry to assault the English lines. The effectiveness of the crossbowmen was limited by rain having soaked the strings of the crossbows, reducing their effectiveness. The English archers had been able to keep their bow strings dry and only used them when the crossbowmen were in range. This led to the massacre of the crossbowmen and a retreat of the survivors, who were then trampled by the advancing French cavalry. This also disrupted an already disorganized advance after a long march to the battlefield by the cavalry. The piecemeal assault of the French forces would lead to an English victory.

Battle of Morgarten
In 1315, Swiss peasants, archers, and infantry at Morgarten were able to ambush a larger Austrian force. The Swiss had rebelled against Austrian rule and funneled the Austrian forces into easily defended passes in the Swiss mountains. The peasants and archers on the high ground effectively rained down arrows and rocks to disorganize the Austrian forces and the infantry charged in forcing the advance guard to retreat into the main body causing more confusion, as well as a general military retreat by the Austrian military.

Battle of Auberoche
In 1345, an English army of about 1,200 men had been moving through the Périgord region of Gascony. The French army had caught up outside the town of Auberoche but did not know the English had hidden in the woods near where the French had encamped upon arrival. During the evening meal the French were surprised by an attack under the cover of English archers. The disorganized French forces were slaughtered and had no choice but to withdraw.

15th to 18th centuries: Generally the savanna cavalries of West Africa used a combined arms approach, seldom operating without supporting infantry.
The French army of the Valois kings, composed of heavily armoured gendarmes (professional versions of the medieval knight), Swiss and Landsknecht mercenary pikemen, and heavy cannons took form during the transition from the medieval way of war to the early modern period.
The late 15th century saw the development of combined pike and shot formations in Europe, starting with the colunelas of the Spanish general Gonzalo Fernández de Córdoba, evolving into the tercios of Hapsburg Spain and the Imperial Army of the Holy Roman Empire during the 16th century.