Ply (game theory) consists of one proposed move by the machine and one anticipated reply by the opponent"). In computing, the concept of ply is important because one ply corresponds to one level of the game tree. The Deep Blue chess computer which defeated Kasparov in 1997 would typically search to a depth of between six and sixteen plies to a maximum of forty plies in some situations. Ply (game theory) In two-player sequential games, a ply is one turn taken by one of the players. The word is used to clarify what is meant when one might otherwise say "turn". The word
Deep Blue versus Kasparov, 1997, Game 6 first time that a computer had defeated a World Champion in a match of several games. This, as well as the fact that Kasparov had lasted only 19 moves in a game lasting barely more than an hour, attracted much media attention. White: Deep Blue Black: Garry Kasparov Opening: Caro–Kann Defense, Steinitz Variation ("ECO" B17) 1. e4 c6 2. d4 d5 3. Nc3 dxe4 4. Nxe4 Nd7 5. Ng5 (see diagram) 5... Ngf6 6. Bd3 e6 7. N1f3 h6? (see diagram) 8. Nxe6! 8... Qe7 9. 0-0 9... fxe6 10. Bg6+ Kd8 11. Bf4 (see diagram) 11... b5? 12. a4