[xrisk]

How is the game state not just the board state? Move history doesn’t matter in chess (FEN encodes the 50 move rule)

[andrewaylett]

Per Wikipedia, it doesn't encode the threefold repetition rule.

https://en.wikipedia.org/wiki/Forsyth%E2%80%93Edwards_Notati...

[anamexis]

Indeed, the 50 move rule, as well as castling rights, whose move it is, and whether any pawns are currently eligible for en passant.

[kzrdude]

Unfortunately move history does matter

[michaelmarkell]

Timing of moves