The 50 move rule

It was recognized early on that some move-limiting rule was needed because otherwise, some chess games could go on forever, which sucks all the fun out of the game and makes tournaments unmanageable.

A famous chess-playing Spanish monk named Ruy Lopez wrote a book in 1561 that proposed the 50-move-limit rule. The move counter is reset to zero if the chessboard changes in an irreversible way (a capture or a pawn move).

Since then, over a long course of time, players tried using higher limits and lower limits. They tried having the limit vary depending on the type of endgame.

But in the end, it was decided that Ruy Lopez was right. Having a simple limit of 50 moves was better than having complex rules that could vary. The fixed 50-move limit was in that sweet spot that worked acceptably well for all endings. It gave the advantaged player a reasonable opportunity to win (even though it’s known that some endgames, with perfect play, require over 50 moves to force checkmate). At the same time, it did not make the game intolerably long for the defending player.

Thus the main goal was achieved: Chess games can end before either player collapses from exhaustion.