From: Michael Trent <shogi <at> GLOBALNET <dot> CO <dot> UK>
Date: 19 apr 1996
Subject: Re: Mate by pawn drop illegal

>I don't know why it's illegal.  However, a possible reason occurred to
>me.  As the endgame approaches, both players are likely to have pawns
>in hand.  Especially, in games of the great masters, they seem to toss
>pawns back and forth like hot potatoes.  Perhaps, it was felt that
>allowing mate with a pawn drop lessened the skill of the game.  Pawns
>are just so numerous by the endgame that no skill is required to have a
>few in hand. Thus, the proverb: "If there is a mate with a Pawn drop,
>there is a legal mate as well" forces the player to look for that
>clever sequence where the pawn is not used last.

I think the idea of the rule is that in certain Tsume-Shogi problems you
have to avoid promoting a Bishop, Rook or Pawn where without the rule there
would be not reason not to do so. I think in this way it serves a similar
purpose to the stalemate rule in Chess, which enables composers to compose
problems where you must promote to a Bishop or Rook.

+------------------------------------------------------------------------------+
|  "Faster, faster! my body is telling me"... The combined attack and defence  |
|  required after 59.P*8b must have had the sweat dripping from their brows... |
+------------------------------------------------------------------------------+
| From 'Encounter at Tenryu Temple' - SHOGI magazine Issue 26 July 1980 page 18|
+------------------------------------+-----------------------------------------+
|          Michael Trent             |           shogi <at> globalnet <dot> co <dot> uk         |
+------------------------------------+-----------------------------------------+