[Event "Soviet Union"] [Site "?"] [Round "0"] [White "Petrosian"] [Black "Kupreichik"] [Result "1-0"] [ECO "D10"] [Opening "Slav: Exchange, 4.Nc3 Nf6"] 1. d4 d5 2. c4 c6 3. cxd5 cxd5 4. Nc3 Nf6 5. Nf3 Nc6 6. Bf4 e6 7. e3 Bd6 8. Bg3 {This retreat allows White to recapture with the h-pawn and open a file in the event that Black chooses to capture at g3.} 8... Ne4 {A violation of the opening principle that one should generally not move a single piece twice in the opening before completing development.} 9. Nxe4 dxe4 10. Nd2 { Now Black has to worry about defending the weak pawn at e4.} 10... Bxg3 11. hxg3 e5 12. dxe5 Qa5 {12...Nxe5 13.Qa4+ Nc6 14.Qxe4+} 13. Qb3 {White is w g to give back the pawn at e5, in return for the right to develop his pieces quickly.} 13... Qxe5 14. Be2 Qe7 {Black drops the queen back to defend the b-pawn, thus freeing up the bishop. But the real problem is that he is behind in development.} 15. Rc1 O-O {Black falls into a trap. Castling should be done early in the game, but not after the h-file is already open!} 16. Nxe4 Qxe4 17. Bd3 Qb4+ {Perhaps Black counted on this move to solve his problems. 17...Qxg2 18.Bxh7+ Kh8 19.Be4+ Qxh1+ 20.Bxh1} 18. Qxb4 Nxb4 19. Bxh7+ Kh8 20. Bb1+ { White has two pawns for the piece but more importantly his pieces are in no position to defend the king because they have never entered the game.} 20... Kg8 21. Rc4 {Black probably missed this rook lift when he castled. White's idea is to play Rch4 and Rh8 mate.} 21... a5 22. Bh7+ Kh8 23. Bf5+ { Black resigned as mate in unavoidable.} 1-0