From: John Kenney <KENNEY <at> EMBL-HEIDELBERG <dot> DE>
Date: 21 feb 1993
Subject: shogi problem revisited

Opps, it seems my analysis was too quick. I not only assumed that the
only king on the board was white's, but also the night and the lance!
So, let's take a look once more at the position
>
>    9    8    7    6    5    4    3    2    1
> +--------------------------------------------+       White in hand:
> |    |    |    |    |+bB |    |    |    |    |  a   +----------------+
> +--------------------------------------------+      | N N L P P P P P|
> |    |    | wG | wS |    |    |    |+bR |    |  b   | P              |
> +--------------------------------------------+      |                |
> |    | wK |    | wP |    |    |    |    |    |  c   |                |
> +--------------------------------------------+      +----------------+
> |    |    | wP |    |    |+wB | wR |    |    |  d
> +--------------------------------------------+
> |    | bN | bL |    |    |    |    |    |    |  e
> +--------------------------------------------+
> |    |    |    |    |    |    |    |    |    |  f    Black in hand:
> +--------------------------------------------+      +----------------+
> |    |    |    |    |    |    |    |    |    |  g   | N L G S P P P P|
> +--------------------------------------------+      | P P P          |
> |    |    |    |    |    |    |    |    |    |  h   |                |
> +--------------------------------------------+      |                |
> |    |    |    |    |    |    |    |    |    |  i   +----------------+
> +--------------------------------------------+
 
As was pointed out earlier, what is the rest of the board like? This is
important, because that will to some extent determine the play. At this
point in the game the material is not important, mating the king is.
There is no Tsume (forced mate) that I can easily find for Black, so he
should look for Hishi (brinkmate). It is important to hem the king first
in order to deliver mate (otherwise he simply runs away). One example of how to
procede (assuming that black's king is not under threat of mate) is to drop
a silver at 9e. This threatens mate with the next move of G'9c. Also, even if
white tries to open up a line of escape with px7e, then G'8d forces the white
king back to 9b or 8b where it will soon be trapped and mated: for example,
K-8b, G-9c, K-7a, N'8c, K-8a, +Bx6b (not a check, but continues forced
response with threat of +Bx7b mate or S'9b mate), Gx6b, S'8b, K-7b, S-7a+ mate.
There are other variations, but the important aim here is to keep the king
hemmed in preferably with checks or forcing (albeit non-check) Hishi type moves
until you can deliver the coup de gras. This is a fun position to analize,
and is well worth looking at in terms of one of the shogi proverbs which
a fellow Shogi-L member and friend as often used against me, "squeeze,
then mate".
                John.
                InterNet: Kenney <at> EMBL-Heidelberg <dot> DE