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I'm working on a checkers software program and I need to implement the official rules including all possible draws. Following this document, at 1.32.2 it states that the game may end up in a draw, if:

  • "Neither player has advanced an uncrowned man towards the king-row during their own previous 40 moves."
  • "No pieces have been removed from the board during their own previous 40 moves."

As I understand it, a game can be declared draw after exactly 80 moves or 80 plies of neither player advancing. In my program's code I always reason about the game in terms of plies.

My question is: Did I understand this rule correctly? I have some slight doubts, because I know about the fifty move rule in chess and 50 plies seems reasonably, but 80 feels like too much. And I find the wording in the rules to be a bit weird. So a draw in checkers is considered after 40 plies or 80 plies?

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    Just to clarify the situation in chess. The 50-move rule is that a player may claim a draw after 50 moves, that is 100 plies, including the ply in the turn where they claim a draw.
    – Rosie F
    Commented May 12 at 7:23
  • @rosie I did not know that! Thank you! So the rule means 50 moves for each player, or is one move considered a full turn (2 plies)? If the latter is true, then I find it very confusing. Commented May 12 at 9:30
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    50 moves for each player, thus 100 plies (50 White alternating with 50 Black). In chess we number the moves like this: White's 1st, Black's 1st, White's 2nd, Black's 2nd and so on. Not White's 1st, Black's 2nd, White's 3rd, Black's 4th.
    – Rosie F
    Commented May 12 at 9:55
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    Indeed the notation of moves, turns and plies is confusing in many situations. Sometimes also tricks, rounds and even games can be confusing.
    – Cohensius
    Commented May 12 at 12:05

1 Answer 1

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Yes, a Draw is considered after 80 plies (40 turns).

The rules says "their own previous 40 moves", which is equal to 40 plies of each player.

From Definition of a Draw 1.32.2:

  1. Neither player has advanced an uncrowned man towards the king-row during their own previous 40 moves.
  2. No pieces have been removed from the board during their own previous 40 moves.

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