This game raised some questions over how best to employ the Medcalf defense, which Black used in this game beginning with 16.d5 to try to keep White from reaching the upper left of the board. Black had played a strong opening game, limiting White so that White had only the left hand margin of the board available to work with. So if the Medcalf defense proved to be successful, Black would almost certainly win the game. Normally it would be successful in this configuration because White had no "helper" pieces available between h10 and either the top or the right side of the board. However, the peg at c3 is an unusual occurrence not normally present when the Medcalf defense is employed, and White believed this would enable the defense to be countered in the event Black should play it. At this point pete99 (White) did not know that David (Black) had learned the defense directly from its inventor, Steven Medcalf, and David did not know that the defense had originally come about because of Steven Medcalf's post-analysis of one of pete99's losses long ago. Pete99 has probably *lost* using the Medcalf defense more times than most players have ever even attempted using it, and so was well-versed in the conditions under which it does not work before playing in such a way as to give Black the option of invoking it.
In the actual game, pete99 did successfully counter the defense for the win. Afterward, Steven Medcalf questioned whether or not there might be a possible win for Black that had been overlooked. To help answer that question, White agreed to begin the analysis by outlining the variations he had considered in response to 16.d5. White's plan was to build on a straight line from d7 because he believed that the only way to win involved having a pair of pegs at j4 and j8.
VARIATION 1: 17.f618.f419.h520.i521.j4 as before, then 22.k4. Normally, White must then go to 23.l3, and a likely loss, but here, because of the c3 peg, that is not necessary. If 23.h9 then Black can move 24.i3, but 25.e4 gives White two paths to connect, using either g2 or c5 for a winning connection. But what if Black moves 26.d3, blocking access to g2 and threatening a win with a link from d3 to b2? White can then move 27.e2, restoring the option of connecting two ways using again either g2 or c5 for a winning connection. If 28.f2 then 29.c5. That concludes Variation 1, but if 28.c729.g3 then things get more complicated. White must threaten to build from h9 to defeat Black -- see Variations 2, 3 and 4.
OTHER VARIATIONS: Some options end with White connecting from h9 to the peg at d7 via f8.
On
2009-08-19 at 04:31,
honest1abe
said:
That is a good analysis. If we back up a few moves to 17.f6, black has a better play with 21.j4 I can find no continuation for white that wins from here. Any suggestions?
On
2009-08-21 at 03:10,
pete99*
said:
honest1abe later corrected that |21.j4 was a typo. But first, before addressing his question in the next comment, the VARIATION 3 discussion needs to be finished.
After pete99 discovered, when playing against the Medcalf defense in the usual way (i.e., in this case with |22.k423.h9), that there was no obvious counter to |22.k423.h924.i325.e426.d327.e228.c729.g330.g9, he was close to giving up on his approach of playing the 15.d7 move that would permit Black to employ the Medcalf defense in the first place. However, because there were no other obvious good alternatives to 15.d7 he looked for any other way to make the 15.d7 move work. And found one... by reversing the direction of the |22.k423.h9 link to |22.k423.e10 instead! This creates VARIATION 4 for White to use instead of either VARIATION 2 or VARIATION 3.
17.f6 Is where Black had the opportunity where I made a typo earlier. So white plays 17.f6 black plays 18.i5. Can anyone see a line that wins for white after that?
In the actual game, pete99 did successfully counter the defense for the win. Afterward, Steven Medcalf questioned whether or not there might be a possible win for Black that had been overlooked. To help answer that question, White agreed to begin the analysis by outlining the variations he had considered in response to 16.d5. White's plan was to build on a straight line from d7 because he believed that the only way to win involved having a pair of pegs at j4 and j8.
VARIATION 0: The game as it actually played out, which is the outcome White had expected. 17.f6 18.f4 19.h5 20.i5 21.j4 22.e10 23.h9 24.g9 25.j8 26.k6 27.m7
VARIATION 1: 17.f6 18.f4 19.h5 20.i5 21.j4 as before, then 22.k4. Normally, White must then go to 23.l3, and a likely loss, but here, because of the c3 peg, that is not necessary. If 23.h9 then Black can move 24.i3, but 25.e4 gives White two paths to connect, using either g2 or c5 for a winning connection. But what if Black moves 26.d3, blocking access to g2 and threatening a win with a link from d3 to b2? White can then move 27.e2, restoring the option of connecting two ways using again either g2 or c5 for a winning connection. If 28.f2 then 29.c5. That concludes Variation 1, but if 28.c7 29.g3 then things get more complicated. White must threaten to build from h9 to defeat Black -- see Variations 2, 3 and 4.
VARIATION 2: 17.f6 18.f4 19.h5 20.i5 21.j4 as before, then 22.k4 23.h9 24.i3 25.e4 26.d3 27.e2 28.c7 29.g3. If 30.f8 then 31.c9 32.e10 33.d12 34.e11 35.d11 36.f13 37.h13 38.g10 39.c14 40.e15 41.d17 42.e16 43.b18, and White can win from there.
VARIATION 3: 17.f6 18.f4 19.h5 20.i5 21.j4 as before, then 22.k4 23.h9 24.i3 25.e4 26.d3 27.e2 28.c7 29.g3. If 30.g9 then ? (Black may win?) TBD
OTHER VARIATIONS: Some options end with White connecting from h9 to the peg at d7 via f8.
I can find no continuation for white that wins from here. Any suggestions?
After pete99 discovered, when playing against the Medcalf defense in the usual way (i.e., in this case with |22.k4 23.h9), that there was no obvious counter to |22.k4 23.h9 24.i3 25.e4 26.d3 27.e2 28.c7 29.g3 30.g9, he was close to giving up on his approach of playing the 15.d7 move that would permit Black to employ the Medcalf defense in the first place. However, because there were no other obvious good alternatives to 15.d7 he looked for any other way to make the 15.d7 move work. And found one... by reversing the direction of the |22.k4 23.h9 link to |22.k4 23.e10 instead! This creates VARIATION 4 for White to use instead of either VARIATION 2 or VARIATION 3.
VARIATION 4: 17.f6 18.f4 19.h5 20.i5 21.j4 as before, then 22.k4 23.e10 24.i3 25.e4 26.d3 27.e2 28.c7 29.g3 for a White win. Or alternately White wins by 26.c7 27.g3.
|18.e10 19.h9 20.i5