Today I Learned

Standardization of rules

The modern rules and appearance of pieces evolved slowly, with widespread regional variation. By 1300, for example, the pawn had acquired the ability to move two squares on its first turn, rather than only one at a time as it did in shatranj. But this rule did not win general acceptance throughout Europe for more than 300 years.

Chess made its greatest progress after two crucial rule changes that became popular after 1475. Until then the counselor was limited to moving one square diagonally at a time. And, because a pawn that reached the eighth rank could become only a counselor, pawn promotion was a relatively minor factor in the course of a game. But under the new rules the counselor underwent a sex change and gained vastly increased mobility to become the most powerful piece on the board—the modern queen. This and the increased value of pawn promotion added a dynamic new element to chess. Also, the chaturanga piece called the elephant, which had been limited to a two-square diagonal jump in shatranj, became the bishop, more than doubling its range.

Until these changes occurred, checkmate was relatively rare, and more often a game was decided by baring the king. With the new queen and bishop powers, the trench warfare of medieval chess was replaced by a game in which checkmate could be delivered in as few as two moves.

The last two major changes in the rules—castling and the en passant capture—took longer to win acceptance. Both rules were known in the 15th century but had limited usage until the 18th century. Minor variations in other rules continued until the late 19th century; for example, it was not acceptable in many parts of Europe as late as the mid-19th century to

From https://www.britannica.com/topic/chess/History