Pike and shot is a historical method of infantry combat, and also refers to an era of European warfare generally considered to cover the period from the Italian Wars (1494 to 1559) to the evolution of the bayonet in the late seventeenth century. The infantry formations of the period were a mix of pikemen and "shot" (arquebusiers or musketeers), with the earliest firearms in the formations using the slow and unwieldy matchlock technology.
Each troop type had a function to fulfill, and supported the other in battle. The shot dealt out casualties at a distance, the pikemen protected the shot from enemy cavalry and were able to close with the enemy. Adoption of this mixed formation permitted the widespread use of firearms—as long as firearms were short-ranged, slow-firing and cumbersome, they would need the protection of the pikemen to survive on the open battlefield.
Pike and shot tactics evolved continually as firearms technology became more advanced, until the flintlock musket and the bayonet cured many of the traditional shortcomings of the "shot" toward the end of the seventeenth century. At that point, the pike and shot formation was phased out in favor of more responsive and maneuverable formations.
The arrival of Grantville in 1631 hastened the decline of pike and shot tactics. Not only was the ring bayonet introduced decades earlier than in the OTL, but infantry firearms quickly advanced to a 19th century level with the introduction of rifled muskets such as the SRG and cap-lock weapons such as the Cardinal breech-loading rifle.
By 1636, with the exception of Spain, the armies of Europe and the Middle East had discarded pike and shot tactics in favor of tactics designed to maximize the effectiveness of the new weapons.