A pike is a very long thrusting spear formerly used in European warfare from the Late Middle Ages and most of the early modern period, and were wielded by foot soldiers deployed in pike square formation, until it was largely replaced by bayonet-equipped muskets. The pike was particularly well known as the primary weapon of Swiss mercenary and German Landsknecht units. A similar weapon, the sarissa, had been used in antiquity by Alexander the Great's Macedonian phalanx infantry.
The pike was a long weapon, varying considerably in size, from long. Generally, a spear becomes a pike when it is too long to be wielded with one hand in combat. It was approximately in weight, with the 16th-century military writer Sir John Smythe recommending lighter rather than heavier pikes. It had a wooden shaft with an iron or steel spearhead affixed. The shaft near the head was often reinforced with metal strips called "cheeks" or langets. When the troops of opposing armies both carried the pike, it often grew in a sort of arms race, getting longer in both shaft and head length to give one side's pikemen an edge in combat. The extreme length of such weapons required a strong wood such as well-seasoned ash for the pole, which was tapered towards the point to prevent the pike from sagging on the ends, although drooping or slight flection of the shaft was always a problem in pike handling. It is a common mistake to refer to a bladed polearm as a pike; such weapons are more generally halberds, glaives or voulges.
The great length of the pikes allowed a great concentration of spearheads to be presented to the enemy, with their wielders at a greater distance, but also made pikes unwieldy in close combat. This meant that pikemen had to be equipped with an additional, shorter weapon such as a dagger or sword in order to defend themselves should the fighting degenerate into a melee. In general, however, pikemen attempted to avoid such disorganized combat, in which they were at a disadvantage.