Abe Yanofsky - Mikhail Botvinnik, Groningen, Netherlands, 1946, was the most popular guess for the topic of my previous lecture on The most famous game in Canadian chess history. For Yanofsky's most famous game, the 14 year old was representing Canada at the 1939 Olympiad. In 1941 at his home town of Winnipeg, Manitoba, he won his first Canadian Championship. In 1943, the Maritimes took advantage of Yanofsky's Navy posting by hosting the Canadian Championship in Dalhousie, New Brunswick. In the final round of the 12 player Round-Robin, the two players with perfect scores met, with Yanofsky beating Charles Smith.
Throughout the Second World War, Holland was a friend of Canada. Canada hosted the Netherlands' Queen Juliana. She gave birth at the Civic Hospital in Ottawa, where the delivery room was declared not to be Canadian territory, so that Princess Margriet could be a Dutch citizen. The street next to the hospital was named Holland Avenue. Canada liberated Holland from the occupying Germans. Afterwards, Holland sent Canada a thank you gift that is still appreciated: tulips. So, Canada's Abe Yanofsky was invited to play at Groningen in the Netherlands in 1946.
With the war over, chess activity and chess tournaments resumed. Groningen was the first major post-war chess tournament, and also the most prestigious of these. Mikhail Botvinnik set out from Russia to prove his claim to the title of the world's strongest chess player. His aim was to wrest the title from World Champion Alexander Alekhine, and after the latter's death earlier that year, to claim the title. Former World Champion Machgielis (Max) Euwe of the Netherlands also aimed to prove himself worthy to reclaim the title he held from 1935-7, while trying to win this important event at home for his nation.
The event was a 20 player round-robin. FIDE awarded Grandmaster (GM) and International Master (IM) titles starting in 1950. Of these 20 players, 11 were awarded the GM title in 1950 (Ossip Bernstein, Isaac Boleslavsky, Mikhail Botvinnik, Max Euwe, Salo Flohr, Alexander Kotov, Miguel Najdorf, Vasily Smyslov, Laszlo Szabo, Savielly Tartakower, Milan Vidmar). Eight, including Daniel Abraham Yanofsky, were awarded the IM title in 1950 (the other were: Arnold Denker, Carlos Guimard, Čeněk Kottnauer, Erik Lundin, Albéric O'Kelly de Galway, Herman Steiner, Gösta Stoltz).
Botvinnik was in a tight race for first place with Euwe. After 14 rounds they were tied for first, well ahead of the others. Thus, Botvinnik needed to win every game, even with Black. In Round 15, he chose his opening defence for its chances for counter-play and victory.
Daniel Abraham Yanofsky - Mikhail Botvinnik
Groningen, Netherlands, 1946, Round 15
Ruy Lopez (C99)
1. e4 e5
This move surprised Yanofsky, as he had been expecting Botvinnik's favourite French Defence. 
2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 5. O-O Be7
(This, the Closed Variation, is much more suited to Botvinnik's style than 5... Nxe4, when Black may get a good game, but is compelled to follow the dictates of White, who has a wide variety of ideas. )
6. Re1 b5 7. Bb3 d6 8. c3 O-O 9. h3
(9. d4 leads to a tricky position after 9... Bg4 10. d5 (an alternative is 10. Be3) 10... Na5 11. Bc2 c6. )
(The defensive set-up 9... Nd7 10. d4 Bf6 leaves Black with a slightly cramped position after 11. Be3. )
10. Bc2 c5 11. d4 Qc7 12. Nbd2
(12. a4 Bd7 gives Black an equal game. )
(Botvinnik would certainly not want the blocked position resulting from 12... Nc6 13. d5 Nd8 14. a4 Rb8 15. c4, though here 15... Bd7 keeps the position a bit more fluid. )
13. cxd4 Nc6 14. d5
(14. Nb3 a5 15. Be3 (15. a4 Nb4 16. Bb1 Bd7 (not 16... bxa4 17. Rxa4 Bd7 as 18. Ra3! gives White an advantage ) 17. axb5 Bxb5 18. Bd2 Nd7 19. Bc3 White had only slight pressure, Yanofsky - Robert Wade, Reykjavik, 1947. ) 15... a4 16. Nbd2 Ba6 (16... Nb4 17. Bb1 a3 preferred by Yanofsky. ) 17. Rc1 Qb7 18. Nf1 Luckis - Miguel Najdorf, Mar del Plata, 1945 is more promising. )
14... Nb4 15. Bb1 a5
Forced, because of the threat of 16. a3 netting the knight, but also good, as the knight may then go to c5 via a6. 
(Also good is 16. a3 Na6 17. b3 (Euwe gives 17. b4 as well worth considering. ) 17... Nc5 18. Ra2 adequately countering Black's pressure along the c-file. )
This position has occurred scores of times. White now decides to exchange his dark-squared bishop for Black's well-placed knight - a double-edged decision. 
(Also good is 17. a3 followed by b3 and Ra2. )
Black is quite prepared to accept the doubling of his b-pawn, in return for which he retains the bishop pair and gets the open a-file. 
(Yanofsky questioned this move. After 18. a3 Na6 (18... Nc2 19. Bxc2 Qxc2 20. Qxc2 Rxc2 21. Bc3! and Black will lose the exchange without adequate compensation, e.g., 21... Rc8 22. Ne3 R2xc3 23. bxc3 Nxe4 24. a4! bxa4 25. c4) 19. b4 and Black's pieces are restricted. )
18... axb4 19. Bd3 Bd8
A common manoeuvre in this type of position - to switch the bishop into the long a7-g1 diagonal. 
(The idea is to force ...Qa5, and then attack the pawn with Ne3-c2, though it does not work out quite that way. White could not reverse the attacking order by playing 20. Ne3 first, as Black could answer 20... Qb7 (or 20... Qa7) 21. Nc2 and protect his pawn with 21... Ba5. ) (If 20. Qb3 Qa5 21. a3 gives White the better game. )
20... Qa5 21. Ne3 b3
A strong and impressive move. 
(After 22. Qxa5 Bxa5 23. Red1 bxa2 24. Rxa2 Bb6. Black has a favourable position due to his bishop pair and White's weak f4 which Black could threaten to occupy with his knight. ) (After 22. axb3 Qxa1 23. Rxa1 Rxa1+ 24. Nf1 Rcc1, Black has an overwhelming position. )
22... Qa4 23. Nd1 b4 24. Ne3 bxa3 25. Rxa3 Nxe4
This is the point of Black's queenside operation. In return for his b-pawn, which is bound to fall, he wins a valuable centre pawn. 
(Not 26. Rxa4 Nxd2 27. Rxa8 Nxf3+ 28. gxf3 Rxa8 which gives Black a clearly superior game. , )
26... Qb4 27. Rxb3 Qa4 28. Bc2 Nc5 29. Rc3 Qb4 30. Qb1 g6 31. Rc4
A survey after the heavy skirmishing shows that Black has the two bishops and a better pawn position. White has a passed pawn, but a dishevelled centre position. If Botvinnik was given time to post his pieces, he would have a superior game. Therefore, Yanofsky embarked on a plan to use this passed pawn to prevent Black coordinating his pieces. , 
31... Qb7 32. b4 Na6
(Better is 32... Na4 and slowly to strengthen the position of his pieces and make his bishops work. )
33. Rxc8 Rxc8 34. Bd3
Black has a distinct positional advantage thanks to his opponent's weak b- and d-pawns. He should now continue with 34... Rb8 (or 34... Bb5). Instead he unaccountably takes the b-pawn at once and allows his opponent to get a decisive pin on his knight. 
34... Nxb4?  
(Black swallows the bait. It is difficult to visualize what consideration prompted Botvinnik to make this fatal capture, especially since after 34... Bb5 (or 34... Rb8) he would have kept the advantage. , ,  E.g., 35. Re2 (If 35. Bc2 Black can continue with 35... Rb8  (or play 35... f5 with the threat of ... f4. )) (Another possibility is 35. Rd1 Bxd3 36. Qxd3 Nxb4 37. Qb3 Rb8 38. Rb1 Qc7 39. Qa4 when Black has a better position, though White has some counter-chances. ) 35... Bxd3 36. Qxd3 Nxb4 37. Qb1 Qa6. ) (34... f5 is met by 35. g4 and if 35... e4 36. Bxa6 Qxa6 37. Nd4 with advantage to White. )
35. Re2!  Ba5? 
(There were still some drawing chances with 35... Rc1+!  36. Qxc1 Nxd3.  This second mistake loses the game. In the correct line, Black's two bishops and consolidated position should ensure a draw. ) (After 35... Rc3 (suggested by fine), there could follow 36. Bc4 Ra3 37. Kh2 e4 38. Nd4 (Fine gives 38. Qxe4 Na2 and Black holds the position.) 38... Bf6 39. Nc6 Ra4 40. Ng4 Bg7 41. Qb3 Bxc6 42. dxc6 Qxc6 43. Bxf7+ Kf8 44. Bg8 d5 45. Bxh7 with a definite advantage for White. )
36. Rb2 Rb8
Black is in an unbreakable pin. 
(Black would get more practical chances by 36... Qb6! 37. Nc2 Rb8 38. Nd2 Nxd3! 39. Rxb6 Rxb6 (but not 39... Bxb6 40. Ne3! Nxf2? 41. Ndc4! Ba7 42. Qc2 winning) 40. Qd1 Bxd2 41. Qxd2 Nf4. )
37. Nd2!  Qa7
(On 37... Bb5 simply 38. Bc4. )
38. Ndc4 Qc5 39. Nxa5 Qxa5 40. Nc2 Nxd3
The best that can be got out of the position, otherwise a whole piece goes. Black has been compelled to cede the exchange after all, and under conditions much less favourable than he could have obtained by sacrificing it on move 35.  Yanofsky's winning play from here on is exemplary and forceful.  Now Black has to give up the exchange in much less favourable circumstances than on move 35. 
41. Rxb8+ Kg7 42. Ne3 Qd2 43. Qf1 Nc5 44. Qd1 Qc3? 
The exchange of queens will lead to the loss of Black's d-pawn if coupled with pinning threats on the seventh rank. 
(In view of his weak d-pawn, Black's position is untenable. But he could have put up more resistance by exchanging queens 44... Qxd1+ 45. Nxd1. As it is, White gets a direct kingside attack. )
45. Rb6 Ba4
(Or 45... Ne4 46. Qb1 Bf5 (46... f5 47. Rb7) 47. g4 Nxf2 48. Nxf5+ gxf5 49. Kxf2 and White's king will escape from the checks with a rook to the good. )
46. Qf3 Qe1+ 47. Kh2 f5 48. Rxd6
(White could have gone in for a knight sacrifice here, e.g., 48. Nxf5+! gxf5 49. Qg3+ Kf7 50. Qh4!. )
(The threat was 49. Nxf5+ gxf5 50. Qxf5 with a mating attack. If 48... Bd7 49. Nc4 f4 50. Qa3 Qxf2 51. Nxe5 with an easy win. )
49. Nf5+! 
An elegant move, paving the way for a quick finish.  The knight sacrifice is even stronger now. 
(If 49... gxf5 50. Qh5 wins quickly. , , ,  50... Nd7 51. Qh6+ Kf7 52. Qe6+ Kg7 53. Qe7+ Kg8 54. Ra6. )
50. Qg4 Ne4
(There is no defence to the threat of 51. Qh4.  If 50... Qe4 51. Qh4!  Qxf5 52. Qxh7+ Ke8 53. Rxg6  and wins. )
51. Qh4!  gxf5
Mate in two was threatened. 
(If 51... Nxd6 White mates in two: 52. Qe7+ Kg8 53. Qg7#. )
52. Qxh7+ Ke8 53. Qg8+
Mate is forced: 53... Ke7 54. Qe6+ Kf8 55. Rd8+ Be8 56. Rxe8+ Kg7 57. Rg8+ Kh7 58. Qg6#.
Meanwhile, Euwe won to pull ahead by a full point. However, Euwe drew his next 3 games, while Botvinnik won all of his to pull ahead by half a point. Both lost their last game. So, Botvinnik recovered from his loss to Yanofsky to win the tournament with 14.5/19, just half a point ahead of Euwe. Yanofsky won the Brilliancy Prize for this game, but finished in 14th place with 8.5 points (+4 =9 -6).
Game notes are from  which uses , ,  and  as sources; and .
Thanks to David J. Ross.