USCF Home arrow Chess Life Online arrow 2009 arrow January arrow The Games of Mark Diesen (1957-2008) : Part II
The Games of Mark Diesen (1957-2008) : Part II Print E-mail
By IM Mark Ginsburg   
January 20, 2009
The March 1977 Chess Life & Review
In the second part of IM Mark Ginsburg's memorial of Mark Diesen (see part i here ), read about Mark in his own words, from a 2002 Chess.FM Radio interview, ‘Inside the Master’s Mind’ (hosted by Tony Rook, file provided by Anthony Boron.) Also play through annotated games from Diesen's big win in the 1976 World Junior Championship.

In His Own Words

Diesen learned chess at nine and credited his dad as being his inspiration in chess. Carl Diesen was a 2200 player, mostly a correspondence player but he once drew versus Walter Browne, having a winning position (OTB).  Mark prepped Carl in that game.  In the databases, it’s given as Mark’s game!  Carl had a huge chess library and  Mark’s interest in chess got Carl back into tournaments. Diesen was born in Buffalo, NY but lived in many places – his dad was in the aerospace industry. 

In Diesen’s first tournament, he only won one game.  He was a little discouraged but he was a natural gamesplayer and very competitive.  He credits the strong Maryland chess community too after he settled in Potomac, MD.  At 12, he played in the Maryland Junior Championship, as the “prodigy” – his competitors were 19 and 20.

Diesen remembers watching every game of the Fischer-Spassky World Championship match on T.V. He was about 2200 at that time.

Diesen was the youngest master in the USA at that time at 15.  At 16, Diesen asked for sponsorship at the Hasting Challengers in England and Ed Edmonson, Executive Director of the USCF, agreed on the unlikely condition that Mark would win – and he did! Diesen beat John Nunn  in an interesting game (presented in this column). People were saying it was a tough tournament and Diesen didn’t have a chance.  Edmondson honored his word and covered Mark's expenses.

 Larry Christiansen usually won American junior events, with Mark Diesen as the perennial second place.  When Larry graduated from the junior category, Mark started winning the U.S. youth events including the 1976 Junior.  To be accurate, Mark actually tied with Michael Rohde in 76.  Mark was awarded the World Junior spot because he was older than Rohde and wouldn’t have an another chance to play.

The ’76 World Junior in Groningen, Holland was a strong event which included Georgiev, Mestel, Ftacnik and Vladimirov. In the first round, Diesen played an IM! Kavalek, also Fischer's assitant, coached Diesen.

Diesen had fond memories of his chess adventures abroad. In Karlovac, Diesen missed a GM norm by ½ point but still won the tournament to become an IM!  Former World Championship Euwe gave him the trophy.  Diesen played in a nice resort in Polanica Zdroj. He won the event but could not take the money out of the country. So he went to the store and realized that his prize could cover 15 color TV sets.  Diesen gave most of his Zlotys to a nice family he met.  He was 19 or 20 at the time.

Diesen also liked playing in Yugsolavia a lot.  The people really liked chess.  But one unfortunate incident occurred when Diesen took a cab to the airport. The taxi driver drove him to the airport, stopped the vehicle, and demanded $150 or $200 or he would tell a police officer Diesen had done something wrong.  He said you can’t speak the language so you can’t dispute what I said.  Diesen was in a hurry and was not planning on this situation, and handed the cab driver a lot of money.

Diesen returned from Europe at 21 or 22.  He played chess for a little bit longer. He never really planned to leave chess. In 1981/82, he enrolled in University of Tennessee in Knoxville, a big engineering school where he majored in chemical engineering. He worked for Shell in New Orleans as a petroleum engineer and lived in New Orleans for eight years. He got married, and had three daughters.

Alfred Carlin, a 2300, was the strongest player there, and Diesen was 7-0 versus him.  In a bizarre footnote, one of Diesen’s coworkers at Shell was Paul Morphy, a direct descendant of the famous Paul Morphy!  Diesen lived in Metarie, LA.  (next to N.O.)   He also lived on North Shore, Covington.   Diesen then moved to Texas in Houston, Woodlands. 

Diesen pointed out that he was a hair’s breadth away from a GM title, and some of his norms expired. In this 2002 interview, he expressed interest in trying for it in American norm events. Diesen had a plus score versus many famous American Grandmasters: John Fedorowicz, Michael Rohde, Joel Benjamin, Nick DeFirmian, Walter Browne, Larry Christiansen and Yasser Seirawan.  Mark pointed out he lost very few games to these players.

Mark Diesen in a high school yearbook photo
More Games

In the first part of this article,
I gave an overview of Diesen's style and examined his early wins including those against DeFirmian, Browne and Torre.

Let’s see some more crisp and solid Diesen victories along with some miniatures and some nerve-wracking blunder fests!  In short, all part of the regular tournament player’s diet!

In the first game, Diesen defeats a well known future GM and author in the Hastings Challengers.  Winning this event gave Diesen the right to play in the Hastings GM group the next year in 1974.

1.e4 g6 2. d4 Bg7 3. Nf3 d6 4. Be2 Nd7 5. Nc3 c6 6. a4 Nh6 7. h4 c5 8. h5 cxd4 9. Nxd4 Nc5 10. Bb5+ Bd7 11. Be3 Qa5 12. Kf1 Rc8 13. Nb3 Nxb3 14. cxb3 Bc6 15. Qd5!?

Position after 15.Qd5

15. Rh3!? a6 16. Kg1 with an edge because 16...axb5 17. axb5 Qb4? 18. Ra4! snares the queen.
 15... Qxb5+
15... Qc7 16. f3 Qd7 17. Bxc6 bxc6 18. Qd2 Ng8 19. b4 Qb7 20. b5 keeps pressure.
 16. Qxb5 Bxb5+ 17. axb5 Ng4 18. Bxa7 Kd7?
By far the best chance was 18... Bxc3 19. bxc3 Nf6 20. Ke2 gxh5 21. c4 Nxe4 22. Be3 Nf6 23. Ra7 Rg8.
 19. f3 Ne5 
Again, Black should think about taking on c3.
 20. Ke2 f5 21. Bd4! 
Now White  has a huge edge.
 21…Rhg8 22. Ra7 Rb8 23. hxg6 Nxg6

The text leads to a losing ending but 23... hxg6 24.Nd5 is not much better. 
24. Nd5 fxe4 25. fxe4 Nf7 26. Bc3 Bxc3 27. bxc3 Rg7 28. Nb4 24. Bxg7 Rxg7 25. exf5 Nf4+ 26. Ke3 Nxg2+ 27. Ke4 e6 28. f6

Very strong was 28. fxe6+ Kxe6 29. Nd5 Kf7 30. Rh6! crushing
28... d5+ 29. Kd4 Rf7 30. Ke5 h5
30... Kc7 31. Kxe6 Rbf8 32. Nxd5+ Kb8 33. Ra4
 31. Na4 Ke8 32. Rxh5 Ne1 33. Rh8+ Rf8 34. Rxf8+ Kxf8 35. Kxe6 Nxf3 36. Nb6 Nd4+ 37. Kxd5 Rd8+ 38. Kc4 Nf5 39. Ra8 Ne3+?

Position after 39...Ne3

39... Rxa8 40. Nxa8 Kf7 is better and White  should win but he needs to work a bit.
 40. Kc5 1-0

In the next game, Diesen reduces veteran Grandmaster Shamkovich to total paralysis in the early middlegame, not easy to do,  and easily converts a crushing ending. 

1. e4 g6 2. d4 Bg7 3. Nf3 d6 4. Nc3 Nf6 5. Be2 O-O 6. O-O c6 7. Re1 Qc7 8. e5! 

Position after 8.e5

A strong and natural expansion.
8 … dxe5 9. Nxe5 Rd8
It’s not an easy life for Black either after 9... Nbd7 10. Bf4 Nxe5 11. dxe5 Nd5 12. Nxd5 cxd5 13. Qxd5 Be6 14. Qe4 Qb6 15. Bf3.
10. Bc4 Nd5 11. Qf3 
White has very unpleasant pressure.
Dangerous looking was 11... Be6 12. Ne4 (maybe the best is 12. Bg5! Bxe5 13. Rxe5 Nd7 14. Ree1 N7f6 15. Bxf6 Nxf6 16. Bxe6 fxe6 17. Rxe6 Rxd4 18. Rae1 and White  maintains a solid plus) 12... Bxe5 13. dxe5 Qxe5 14. Bg5 Nd7.
12. Ne4 Rf8 13. Bxd5! 
Now it really gets bad for Black.
13…cxd5 14. Nf6+Bxf6
14... Kh8 15. Bg5 Nd7 16. Nexd7 Bxd7 17. g4
15. Qxf6 Qd8 16. Ng4 Qxf6 17. Nxf6+ Kh8
17... Kg7 18. Ng4
 18. Bh6 Rd8 19. Re3

  Of course, this is dreadful for Black.  Watch Diesen effortlessly reel his victim in. 
19….Nd7 20. Bg5 Rf8 21. Bh6 Rd8 22. Bg5 Rf8 23. Rc3 Nxf6 24. Bxf6+ Kg8 25. Rc7 b6 26. a4 Ba6 27. Ra3 Rfc8 28. Rac3 Rxc7 29.Rxc7 Rc8 30. Rxa7 Rxc2 31. h4 Bc8 32. b4 Kf8 33. Bd8!

Position after 33.Bd8

e5 34. Bxb6 exd4 35. Bxd4 Rc1+ 36. Kh2 Rc4 37. Bc5+ Kg7 38. Rc7 Be6 39. a5 d4 40. a6 d3 41. Rc6 Rxh4+ 42. Kg1 Rh5 43. Bd4+ f6
43... Kh6 44. Be3+ Kg7 45. a7
44. Rxe6 Rd5 45. Be3 1-0

The next encounter shows Diesen defeating veteran Minnesota master Curt Brasket with subtle minor piece maneuvers that bring decisive dividends early.

1. c4 Nf6 2. Nc3 d5 3. cxd5 Nxd5 4. g3 c5 5. Bg2 Nc7

5... Nxc3 is playable
 6. Nf3 Nc6 7. Qa4 Qd7

This doesn’t look too healthy.  Black also has to solve problems after 7... Bd7 8. Qb3 Rb8 9. O-O.
8. O-O e5 9. a3 f6 10. e3 Rb8 11. Rd1 b5 12. Qc2 c4 13. d3 
Something went clearly wrong for Black because White  has a significant edge already.
13 ... cxd3 14. Rxd3 Qe6 15. e4
The non-obvious move 15. Nh4! is very strong here.  If 15… g5? (15... Be7 16. Nd5!) 16. Nd5! is crushing.
15... Na5 16. Be3 a6 17. Na2 Na8 18. Nd2 Bb7 19. b4 Rc8 20. Rc3 Nc6 21. Nb3 Be7 22. Nac1! 
Very nice!  White builds up intolerable pressure on Black’s rickety formation.
22 …. O-O 23. Nd3 Kh8 24. Ndc5 Bxc5 25. Nxc5 Qe7 26. Nxb7 Qxb7

Position after 26...Qxb7

27. Bh3!
 Everything is like clockwork. 
27… Rc7 28. Rc1 1-0

One gets the feeling Brasket never knew what hit him.

Now let’s see two convincing solid victories with Diesen playing Black.  In the first, ex-Candidate Borislav Ivkov commits a major inaccuracy early in the Slav Defense.  Diesen gives him one chance to get back in the game but Ivkov misses it.

1. d4 d5 2. c4 e6 3. Nc3 c6 4. e3 Nf6 5. Nf3 Nbd7 6. Qc2 Bd6 7. Bd2 O-O 8.O-O-O Qe7 9. e4 Nxe4 10. Nxe4 dxe4 11. Qxe4 e5 12. c5? 

Position after 12.c5

A bad blunder.  Ivkov must have gotten his lines mixed up.
12… exd4! 13. Qxe7 Bxe7 14.b4 a5
 And just like that, White  has a lost game.  Ivkov keeps fighting and Diesen gives him one chance later…..
15. a3 axb4 16. axb4 Bf6 17. Bd3 b6 18. cxb6 Nxb6 19. Bg5 Bxg5+ 20. Nxg5 h6 21. Nf3 Nd5 22. Nxd4 Nxb4 23. Be4 Ra4 24. Rhe1 c5 25. Nb3 c4 26. Nc5 Ra5 27. Nd7

Position after 27.Nd7

Diesen misses a beautiful way to put Ivkov away.  27... c3!! 28. Nxf8 Ra1+ 29. Bb1 Bf5! and mate!
28. Kb2 Bxd7 29. Rxd7 Rae5 30. Kc3 Na6?  
A serious miscue.  Correct was 30... Na2+! 31. Kb2 Rb8+! 32. Ka1 (If 32. Kc2 f5 33. Bd5+ Rxd5 34. Rxd5 Nb4+ wins – that pesky knight!)
32... Nc3 33. Bh7+ Kxh7 34. Rxe5 Rb1 mate!
31. Kd4??

Position after 31.Kd4

Ivkov makes one more stumble. 31. Rd4 Nc5 32. f3! holds on!
 31... Rxe4+ 0-1

The next game has Diesen totally outplaying veteran Filipino master Roberto Kaimo.

1. d4 Nf6 2. c4 e6 3. Nf3 b6 4. e3 Bb7 5. Bd3 d5 6. Nc3 Bd6 7. O-O O-O 8. Qe2 Nbd7 9. Nb5 Be7 10. Rd1 a6 11. Nc3 Ne4 12. Nd2 f5 13. f3 Nxd2 14. Bxd2 Bd6 15. Be1 Qf6 16. Bf2 Kh8 17. Rf1 c5!

17...c5Kaimo copy.jpg
Position after 17...c5

Seemingly effortlessly, Diesen starts to build a menacing initiative.
18. f4 dxc4 19. Bxc4 b5 20. dxc5 Nxc5 21. Rad1 Rad8 22. Bd3 b4 23. Nb1 e5!

 Everything with gain of time.  Black is on his way to victory.
24. Bc4 Ne4 25. Bd5 Bxd5 26. Rxd5 exf4 27. Rfd1 fxe3 28. Bxe3 Qe6 29. Qd3 h6 30. g3 Nf6 31. Rd4 Ng4 32. Re1

Position after 32.Re1

The latent threats on the b6-g1 diagonal are very nasty.  There is no defense.
33. h3
White is totally overloaded. If 33. Rxd8 Rxd8 34. Qc2 Nxe3 35. Qxc7 Rd3 36. Qb7 Qxa2 and wins.
33... Rxd4 34. Qxd4 Rd8 35. Qc5 Bxg3 36. hxg4 Bxe1 37. gxf5 Qd6 0-1

Before we get into the hard-fought critical games from Diesen’s win at the 1976 World Junior, let’s see for curiousity’s sake some Diesen miniatures.

The following gamelet was against a future IM from Hungary in a game I am sure he will want to forget.

1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 d6 5. O-O b5 6. Bb3 Na5? 7. d4! exd4 8. Qxd4

Diesen was always strong theoretically.  He has reacted properly to Black’s inferior line.  In practice White  has a big plus score from this position.  I bet he was not expecting Black’s next move, though!

Position after 8...c5

9. Bxf7+ Kxf7 10. Qd5+ Ke8 11. Qxa8 1-0
Both young players probably went to get some nice Dutch beer.  In my experience at Dutch and Belgian junior tournaments, this was a definite option after the game.

And here he quickly wins versus the future IM Larry D. Evans (not to be confused with Grandmaster Larry Melvyn Evans).

1. c4 Nf6 2. Nc3 e5 3. Nf3 Nc6 4. e3 Bb4 5. Qc2 O-O 6. Nd5 Re8 7. Qf5 Be7?

Position after 7...Be7

8. Nxe5! 
It’s safe!  All good players know when such pawns are safe.
8…d6 9. Nxc6 bxc6
In this dubious line, Black could try 9... Bxf5 10. Ndxe7+ Qxe7 11. Nxe7+ Rxe7 12. d4 (12. d3 d5 13. cxd5 Nxd5 14. e4 Nb4 15. Kd2 Be6 16. b3 c5) 12... c5 to get some kind of counterplay.
10. Nxe7+ Qxe7 11. Qf4 d5 12. Be2 dxc4 13. O-O Nd5

And here, 13... Be6 14. Bxc4 Bxc4 15. Qxc4 Qd6 limits the damage.
14. Qxc4 Rb8 15. d3 Rb4 16. Qc2 Rh4?
Position after 16...Rh4

This irrational rook lift cannot work.  Kasparov pointed out in an instructional essay that an attack without pawns hardly ever works.
17. e4 Qd6 18. g3 Nb4 19. Qb3 Rh3 20. Bf4 Qe7 21.Qc3
 Here Black had seen quite enough and resigned due to the absurdist placement of most of his pieces.  For example, 21… g5 (21... c5 22. Be3 Na6 23. Rfc1) 22. Be3 Rh6 23. a3 Na6 24. h4 f6 25. Qxc6 is murder.

One more quick one:  Diesen wins against a Yugoslav 2445 player with a strong continuation introduced by his 12th move.

1. d4 d5 2. Nf3 Nf6 3. c4 dxc4 4. e3 c5 5. Bxc4 a6 6. a4 e6 7. O-O cxd4 8. exd4
Nc6 9. Nc3 Be7 10. Re1 O-O 11. Bg5 Qb6?! 12. d5!
Strong. 12. Qd2 Rd8 13. Rad1 Na5 14. Ba2 h6 15. Bf4 Bb4 is not so much.
12... Qxb2
Very interesting but maybe not stronger is 12... Na5 13. Ba2 Qxb2 14. Bd2!? (14. d6!? Bd8 15. Rc1 Nc6 16. Rc2 Qa3 and Black holds on) 14... Rd8 15. Qe2 Bd6 16. Rab1 Qa3 17. dxe6 Bxe6 18. Bxe6 Re8 19. Ra1 Qc5 20. Ng5 fxe6 21. Nce4 Nxe4 22. Nxe4 and White  has good prospects.  After the greedy text grab, the game becomes ultra-sharp.
13. Bd2 exd5 14. Bb3!?  
Interesting, but probably best is the straight-forward 14. Nxd5!  Nxd5 15. Bxd5 Bd6 (15... Bf6 16. Rb1 Qa3 17. Bxc6 bxc6 18. Bb4 Qa2 19. Bxf8 Bf5 20. Bd6 Bxb1 21. Qxb1 Qxa4 22. Bb8!! g6 23. Qb7 winning) 16. Rc1 h6 17. Bc3 with a white plus.
14... Na5?? 
The fatal mistake.  Correct was 14... Ne4! 15. Nxd5(15. Nxe4?? dxe4 16. Rxe4 (16. Rb1 Qf6 17. Rxe4 Bf5 18. Rf4 Bd6 19. Bc3 Qxc3 20. Rxf5 Rad8 21. Qe2 Be7) 16... Bf5 and Black is on top) 15... Nxd2 16. Nxd2 Bd8 17. Re4 g6 18. Nc4 Qg7 19. Nd6 Bf5 20. Nxf5 gxf5 21. Re3 Kh8 22. Rb1 Rg8 23. Rg3 Qe5 24. Qh5 f4 25. Qxe5+ Nxe5 26. Nxf4 Rxg3 27. hxg3 b5  and Black holds on in the ending.
15. Nxd5 Nxd5
There is no escape. Also losing is 15... Nxb3 16. Nxe7+ Kh8 17. Rb1.
16. Bxd5 Bd8 17. Rb1  Black resigned.    1-0

A rout after his blunder on move 14. If 17…Qf6 (17... Qa3 18. Bb4) 18. Bg5 Qg6 19. Bxd8 wins.

Wins From the Junior

Now let’s see some games from Diesen’s 1976 World Junior win.
Diesen receives his World Junior trophy.

In Round 2, a tough Ruy Lopez battle versus the Dutch participant.

1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 5. O-O Be7 6. Re1 b5 7. Bb3 O-O 8. d4
d6 9. c3 Bg4 10. Be3 exd4 11. cxd4 Na5 12. Bc2 c5 13. Nbd2 cxd4 14. Bxd4 Nc6 15. Be3 d5 16. h3 Bh5 17. g4 

Position after 17.g4

Diesen and Kavalek prepared 8. d4!? for the event but modern theory believes it’s innocuous.  For example, here Black has several moves to reach a good game.
17… dxe4
17... d4!? 18. Bf4 d3 (18... Bg6!?) 19. Bb1 Bg6, and perhaps best of all is 17... Bg6! 18. e5 Ne4 19. Rc1 Rc8 and theory showed in later games that Black has no problems.
18. gxh5 exf3 19. Qxf3 Nb4
Stronger looks 19... Nd4! 20. Bxd4 Qxd4 21. Rxe7 Qxd2 22. Bb3 Rae8 23. Rae1 Qg5+ 24. Kf1 Rxe7 25. Rxe7 Qxh5 26. Qxh5 Nxh5 27. Ra7 Nf4 28. Rxa6 Rc8 and Black makes a draw.
20. Bb3 Nbd5 21. Bg5
21. h6 Nxe3 22.hxg7 Kxg7 23. Qxe3 Bc5 24. Qxc5 Qxd2 25. Re7 Kh8 is murky.
21... h6 22. Bh4 Re8? 
Last chance for 22...Ra7! 23. Rad1 Rd7! 24. Qf5 Bb4 25. Ne4 Bxe1 26. Bxd5 Rxd5 27. Rxd5 Bxf2+! And with this surprising tactic Black holds the game.  With the text move, Black winds up in total paralysis.
23. Rad1 Ra7 24. Ne4 Rd7 25. Ng3 Nc7 26. Nf5 Bb4 27. Nxh6+
Black resigned having no wish to see  27… Kf8 28. Rxe8+ Qxe8 29. Bxf6 Rxd1+ 30. Qxd1 gxh6 31. Qc2 and wins. 1-0

Let’s move on to a nervy round four battle versus a future Australian GM, Ian Rogers.  Numerous inaccuracies on both sides make for a very entertaining replay.  Rogers did well in this event, going on to defeat future GM Evgeny Vladimirov in a later round.

1. e4 e5 2. Nf3 Nc6 3. Bb5 Bc5 4. c3 f5 5. d4 fxe4 6. Nxe5

Safe and good for a small edge is 6. dxc5!? exf3 7. Qxf3 Nf6 8. O-O O-O 9. Na3.
6... Nxe5 7. Qh5+ Nf7 8. Bc4 Qe7 9. dxc5 Nf6 10.Qxf7+ Qxf7 11. Bxf7+ Kxf7 12. Bf4 Nd5 13. Bg3 b6!

Position after 13...b6

White’s ‘fancy’ tactics have accomplished zero.  Black is fine here.
14. Na3 bxc5 15. O-O-O Nf6 16. Nb5 d5 17. Nxc7 Bg4 18. Rd2 Rad8 19. h3 Be6 20. Be5 Rd7 21. f3 e3

With 21... exf3 the game is totally level. It is quite conceivable Rogers was going for more.  Soon he gets it, in terms of a big edge.
22. Rd3 Bf5 23. Rxe3 d4 24. Re2 dxc3 25. bxc3?
 It’s not easy for a human to see the computer line of 25. Rd1!! Rxd1+ 26. Kxd1 Bd3 27. Rf2 c2+ 28. Kc1 and it’s completely balanced.
25... Rb8 
Suddenly Black has a huge initiative.  Diesen was probably feeling a bit sick at this point.  Every game is huge at the World Junior.
26. Rb2 Rxb2 27. Kxb2 Rd2+ 28. Kb3 Rxg2
After 28... Nd7! 29. Re1 Nb6!, it is not likely White  would have survived and we would have seen Vladimirov or Ftacnik triumph in this event.
29. Bd6 Nd7 30. Re1 Rd2

30...g5 still keeps some black edge.
 31. Re7+ Kg6?!
Easiest is 31... Kg8 32. Ne8 g6  with equality.
32. Ne8 Rd3 33. Rxg7+ 
Now White  is on top.  But watch what happens!
33….Kh5 34. Re7?

Another misstep in this nervy game. 34. f4! h6 35. Rg1 Kh4 36. Ng7! Be4 37. f5! Kxh3 38. Rg6 and with this attacking sequence, White  keeps a small edge with chances to win!
34... Kh4 35. Bc7 Kxh3?? 

Position after 35...Kxh3

Correct is the coordinating 35... Rxf3 36. Nd6 Bxh3 37. Rxh7+ Kg5 38. Ne4+ Kg6 and Black reaches a safe draw!
36. Nd6 c4+ 37. Kb4
Easier was 37. Kb2 Rd2+ 38. Ka3 and wins.
37... Nb6? 
It is highly surprising the opportunistic Rogers missed the tricky 37... a5+! 38. Kxa5 (38. Kxc4?? Nb6+! 39. Kc5 Nd5 and Black amazingly holds!) 38...Rxf3 39. Nxf5 Rxf5+ CHECK!! 40. Kb4 Nf6 41. Kxc4 and White should win the ending, but at least Black gave White  the chance to go horribly wrong on move 38!
38. Nxf5 Nd5+ 39. Kxc4 Nxe7 40. Kxd3 Nxf5 41. c4 h5 42. Ke4 Ne7 43. Bd6 Nc8
The bishop overmatches the knight and there really is no ‘race’ at all.  Diesen concludes without further adventures.
44. c5 h4 45. Be5 Ne7 46. Bf6 Nc8 47. c6 a5 48. a4 Nd6+ 49. Kf4 Nc8 50. c7 Na7 51. Ke4 Nc8 52. Be5!
Black resigned.  A plausible continuation was 52…Kg2 53. f4 h3 54. f5 h2 55. Bxh2 Kxh2 56. f6 and it’s all over.

The above game gives the reader a good feeling for how incredibly tense such an event must be.  Of course there were easier rounds, such as the following Round 11 annihilation:

1. e4 c5 2. Nf3 d6 3. Bb5+ Nd7 4. d4 Ngf6 5. Nc3 cxd4

5….a6!? is interesting, not playing cxd4 as shown by Bologan.
  6. Qxd4 e6 7. Bg5 Be7 8. O-O-O O-O 9. h4 Nc5 10. Bxf6 gxf6 11. g4 a6 12. Be2 Qe8 13. Qe3 Kh8 14. g5! fxg5
15. hxg5 Rg8 16. Rh5 Rg7 17. e5 d5 18. Nh2 Na4 19. Ng4 

Black has no real counterplay.
 19…Nxc3 20. bxc3 Ba3+ 21. Kd2 d4 22. Qxd4 1-0

Position after 22.Qxd4

A very clean attacking game.

One of the favorites, Vladimirov, was swindled in a winning game incredibly by Ftacnik to lose , collapse in subsequent rounds, and fall out of the winner’s circle.  In the end, Diesen had some luck, some well played games, and also two pieces of luck – first in round 12 versus the Israeli player Nir Grinberg and then in the last round against future GM, Mexican participant Marcel Sisniega. 

To describe the Grinberg game, Kavalek wrote (April 1977 CL&R) :

“… the American did a good job outplaying Grinberg positionally.  All he had to do was collect a few pawns here and there and win the game.  Instead he started playing for his opponent’s time trouble, forcing him to make only defensive moves and suddenly it was Mark who was short of time; the tables turned and at adjournment (!) Grinberg held the advantage.

Yes, they had adjournments in those days. Kavalek continues:

Losing this game would cost Mark the World Junior Championship.  A lot was at stake.  […] And the adjournment was a horrible experience.  First, Grinberg got a position with great winning chances and then he made a few little mistakes and it looked like a draw; later still on my arrival in the tournament hall I was being congratulated because “Diesen will see the two-move combination that leads to a winning pawn endgame. But Mark did not see it; his mind was so fixed on drawing that it did not occur to him that there might be a winning opportunity.”   

As you can tell, quite the nerve-wracking affair.  Here it is (note by Round 12, as you can imagine, both players were probably quite tired):

1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 e6 6. g4 h6 7. g5 hxg5 8. Bxg5 Nc6 9. Bg2 Bd7 10. Nb3 a6 11. Qe2 Be7 12. h4
Position after 12.h4

The author employed this successfully versus John Meyer in a DC Chess League match in the mid 70s.  Objectively, though, it’s nothing – witness the game continuation.
13. O-O-O O-O-O 14. f4 Nh5! 15.Bxe7 Nxe7 16. Qf2 Ng6 17. Ne2?!
Also not much is 17. f5 Ne5 18. Kb1 Kb8 but the awkward text leads to problems.
 17... Kb8 18. Rh3 Bb5 19. Nbd4 Bxe2 20. Nxe2 Qc5 21. Qf1 Rc8 22. Rd2 Qc4 23. Kb1 Nhxf4 24. Rc3 Qb5 25. Rb3 Qa5 26. Rxd6 Qc5

Another way is 26... Qc7! 27. c3 Qxd6 28. Rxb7+ Kxb7 29. e5+ Qd5 30. Bxd5+ Nxd5 31. Qxf7+ Nge7 32. h5 Rhf8 is just bad for White .
27. Rd2 Rhd8 
Black has a huge edge.
28. e5
Position after 28.e5

Why open up the king? Quite clear was 28... Nxg2 29.Qxg2 b5 30. Rxd8 (30. Nc1 Rxd2 31. Qxd2 Nxe5 and White ’s position is in ruins) 30... Qxc2+ 31. Ka1 Rxd8 winning by direct attack.
29. Rc3 Rxd2
29... Qxe5? 30. Qf2!! saves the game!
30. Rxc5 Rxc5 31. Nxf4 Nxf4 32. Be4 Rxe5 33. Kc1 Rd4 34. Qxf4

The unopposed queen has well known cheapo potential, especially in time trouble situations.
 34…Rdxe4 35. Qxf7  Rg4 36. Qf8+ Kc7 37.  Qe7+ Kc6 38. Qe8+ Kc7 39. Qe7+ Kc6 40. Qa7 Rge4 
40... Rxh4 41. Qxa6+ Kc7 is dead equal.
 41. Qxa6+ Kc7 42. b3 Rxh4 43. Qa5+ Kb7 44. a4 Rhh5 45. Qb4
Position after 45.Qb4

This blunder really could have hurt.  Correct was 45... Rhf5! 46. c4 Kc8! 47. cxb5 and now the nice perpetual check mechanism 47…Rf1+ 48. Kc2 Rf2+ 49. Kd3 Rf3+ 50. Kc2 Rf2+ with a draw; the white king cannot hide.
46. Qe4+?? 
Fortunately as Kavalek relates, he was not in the tournament hall at this time – he might have had a heart attack. The simple 46. c4! would give Grinberg every chance of winning.
46... Rc6 47. axb5 Rxb5 48. b4 g5 49. Kb2?? 
Position after 49.Kb2

The pendulum keeps swinging wildly. 49. c3 is equal.
As alluded to by Kavalek, Diesen was so fixated on drawing that he missed the simple 49...Rxb4+! 50. Qxb4+ Rb6 and wins!
50. Kb3 Rf4 51. Qg2 Kb6 52. Qxg5 Rf3+ 53. Kb2 Rfc3 54.Qa5+ 1/2-1/2

What a titanic battle!   Crazy blunders all over the place – both players must have been completely exhausted!

Let’s move on to an equally dramatic last round game versus the Mexican player, future GM Marcel Sisniega.

1.e4 e6 2. d4 d5 3. Nd2 Nf6 4. e5 Nfd7 5. c3 c5 6. Bd3 Nc6 7. Ne2 cxd4 8. cxd4 f6 9. exf6 Nxf6 10. Nf3 Bd6 11. O-O Qc7
Position after 11...Qc7

12. Nc3 a6 13. Bg5 O-O 14. Bh4  Bd7 15. Re1 Rae8 16. Rc1 Qb6 17. Na4 Qa5 18. Nc3
White had the interesting try 18. Nc5!? Nxd4 19. Nxb7! Nxf3+ 20. Qxf3 Bxh2+ 21. Kxh2 Qb4 and maybe Black holds on.  On the other hand, 18. Nc5!? Bxc5?! 19. dxc5 Qxa2?! 20. Bxf6! Rxf6 21. Qc2! threatening to win the queen with Ra1, thus winning the h7 pawn, yields a white plus.
18... Nb4 19. a3 Nxd3 20. Qxd3 Nh5 
White has zero here; another good argument for 18. Nc5!?
21. Bg3 Nxg3 22. hxg3 Qb6 23. Re2 Rf5 24. Rce1 Ref8 25. g4?

Position after 25.g4

A senseless weakening. One can imagine the nervous state of the participants.
What now?  This is just bad for White. Diesen tries a total bluff.
26. Re3 Bf4?
Very safe and convincing was the simple 26... Qxb2! 27. Rb1 Qxa3 28. Rxb7 Qc1+ 29. Re1? (29. Qd1 Qxd1+ 30. Nxd1 Rd8 and Black should convert) 29... Rxf3! and Black wins.  This was the first spot in which Sisniega could have denied Diesen the title.
27. R3e2 Rg6 28. g5 Qd8 29. g3 Bxg5 30. Ne5 Rh6 31. Ng4 Rg6
31... Rh5!  keeps a solid edge.
32. Ne5 Rh6 33. Ng4 Rh5 34. Re5 Be8
34... g6! is a great move.  If the plausible blunder 35. f4?? Black reacts harshly with 35…Bxf4!! 36. gxf4 Qh4! and wins.  The same motif was tried by Black on his next move at precisely the moment where it doesn’t work since the h5 rook is unprotected!  The devil is in the details.
35. Qe2 Bf4?? 
Position after 15...Bf4

Out of pure blindness to White’s reaction or perhaps simple time trouble, Sisniega tosses the game away.  35... Qd7 and 35…Qc8 both kept the balance.
36. Rxh5
To point out the magnitude of Black’s blunder last move, the primitive 36. gxf4 Rxf4 37. Rxh5 Bxh5 38. Nh6+ also wins.
36... Bxh5 37.gxf4 Rxf4 38. Nh6+! 

Position after 38.Nh6+

Did Black really miss this simple check?  It appears so.  Game and title to Diesen!
38….gxh6 39. Qxh5 Qf6 40. Qe8+ Kg7 41. Qxe6 Rxd4 42. Qd7+ 1-0

I hope these games have given a good sense of the interesting and strong chess style of Mark Diesen.  I really have a hard time believing he is gone. RIP Mark C. Diesen 1957-2008