Sometimes, people can play out of character. Vassily Smyslov, who would go on to become World Champion next decade, was known for steering towards quiet positions where he would rely on his superior technique. However, in this 1945 game with Alexander Tolush (White) in the Soviet Championship that year, Smyslov played out of character and courted complications which should have turned out badly for him. Tolush had a golden opportunity to steal a win following an opposite side castling battle.
White started out with the Capablanca Variation of the Nimzo-Indian; however, his intentions were anything but peaceful as he castled queen side and sought to take Smyslov's fortress by storm after blockading the Queen side to delay Smyslov's counterplay.
On move 9, he could have played 9. Nxd4, uncovering his Bishop and preparing to use the f5 square. White could have played 10. cxd5 0-0 11. a3 Bd6 12. Nb5, grabbing the Two Bishops in a wide open position and played for a positional advantage. But he sounded the attack with 13. g4 and 16. h4.
On move 16, Smyslov could have played 16...Nh7!?, stopping the pawn roller in its tracks. He could have also sought to break the blockade with 16...bxc5 17. dxc5 Ne5 18. Nd4 Nfd7 19. g5 hxg5 20. hxg5 Qxg5+ 21. Kb1 Nf8, but that would have been met with 22. Bb5!!, creating headsplitting complications. After 22...cxb5, White would have regained the piece with 23. f4, due to the fork on f4 and c7.
On move 18, wrong would have been 18. gxh6 Qf6! because of Black's counterplay on f3. Tolush saw further than the machine in this position when he played 18. Bh3.
On move 21, Smyslov could have kept the White Bishop off the h2-b8 diagonal with 21...bxc5 22. dxc5 Qc7!
On move 26, another line that the machine found attractive would have fallen short -- 26...Be3 27. Qb4 Bc8 28. Rhe1 Bf2 29. Re2 holds for White.
Fritz's evaluation hovered near equality until move 30 and Smyslov could have maintained the balance with 30...Bf4, trading off the powerful Bishop on d6 and blockading White's pawn storm. However, he uncorked the anti-positional howler 30...g6?, which should have lost the game.
The tactics along the long Black diagonal were tantalizing even for someone of Smyslov's caliber; however, it is rarely a good idea to move pawns in front of one's King while being attacked. A pawn on g6 is frequently a sitting duck for an onrushing h-pawn and White obtained a winning position with 31. h5 Nxd4 32. Rxd4 Qf6.
Tolush could have capped his unlikely victory with 33. hxg6!! Qxd4+ 34. Kb1 Qf6 35. Nh5 Qxg6 36. Bf5 Qg5, when despite being up an exchange, Black is helpless against the threats on the King. It does not require exact calculation to find such a line, just the knowledge that the first person to back down in an opposite side castling battle usually loses.
White backed down with 33. Qb2?, starting his slide towards defeat as Smyslov's pressure down the long Black diagonal suddenly became real. White was still winning as late as move 39, when he could have played 39. f5!, protecting his Knight and hitting the Queen. But he allowed a pin with 39. Qf2? and then fell on his sword the next move with 40. Qxe2?? instead of seeking to hold on with 40. Qg1.