[Event "Mar del Plata"] [Site "?"] [Round "0"] [White "Ojanen"] [Black "Trifunovic"] [Result "0-1"] [ECO "E46"] [Opening "Nimzo-Indian: 4.e3 O-O"] {The less familiar but nevertheless dangerous flank attack on the hanging pawns by ... Pb5} 1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. e3 O-O 5. Nf3 d5 6. a3 Bxc3+ 7. bxc3 c5 8. cxd5 Nxd5 9. c4 Nf6 10. Qc2 cxd4 11. exd4 Bd7 $1 12. Be2 b5 { This strong flank attack is possible, thanks to the fact that White isuncastled } 13. c5 {If White had allowed this pawn to be captured at c4, he would have been left with an isolated d-pawn. The consequences of the move actually played are even more serious, for he now gets all disadvantages which we know are associated with "blockaded security", but not its advantages. The usual advantage lies in the possiblity of an attack on the b-pawn, but in the present case, with a pawn at b7, but already on b5, this simply doesn't arise} (13. cxb5 Bxb5 14. Bxb5 Qa5+) 13... Bc6 14. O-O Be4 { Occupying a vital "vacant central square"} 15. Qc3 (15. Qb3 Nc6 (15... a6) 16. Qxb5 Bxf3 17. Bxf3 Nxd4 18. Qd3 Nxf3+ 19. Qxf3 Qd5) 15... Nc6 16. Be3 (16. -- Bxf3 17. Bxf3 Nxd4 18. Bxa8 Ne2+) (16. Bxb5 Bxf3 17. Qxf3 Nxd4 18. Qd3 Nxb5 19. Qxb5 Qc7 {the weakness of the white c-pawn will be a serious liability}) 16... Nd5 17. Qc1 Rb8 18. Ne5 Qc7 19. Nxc6 Qxc6 20. Bd2 $2 (20. f3 Bg6 (20... Nxe3 21. Qxe3 Bd5 {Black's twofold advantage consists of the weakness of the White d-pawn and his ability to create a passed pawn on the extreme Queen's wing})) 20... Bxg2 $1 21. Re1 (21. Kxg2 Ne3+ 22. Kg3 Qg2+ 23. Kh4 Nf5+ 24. Kh5 g6#) 21... Ne7 22. Bf4 Rb7 23. Bd6 Bd5 24. Qc3 Rc8 25. Bxe7 Rxe7 26. Reb1 e5 $1 27. Bxb5 Qg6+ 28. Qg3 Qe4 29. f3 Qxd4+ 30. Qf2 Qxf2+ 31. Kxf2 Rxc5 32. Bd3 g6 0-1