In discussion surrounding another recent question, the fact came up that a "dropped" pawn in Shogi isn't allowed to deliver immediate checkmate, whereas any other type of piece can be dropped to deliver checkmate. This has gotten me (not a Shogi player at all) wondering why that distinction is in the rules:

Is there a particular rationale, perhaps coming from the other rules of Shogi, for singling out pawns as being unable to deliver checkmate via a drop?

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    >>The rule that a pawn can not give checkmate probably stems from the rule that a piece may not be placed in a position from where it is unable to promote or continue. If that's the case, then dropping a piece on a space from which it can't move because of your other pieces should also be prohibited. For example, dropping a pawn or a lance right behind one of your pieces should be prohibited. – Fein Feb 6 at 12:40

I found this on the web:

The rule that a pawn can not give checkmate probably stems from the rule that a piece may not be placed in a position from where it is unable to promote or continue. A pawn may only give checkmate by being placed directly in front of the emperor; a position from where it is unable to move or promote. It can not take the emperor piece as it could with other pieces, and it can not be promoted until it moves again.

In Shogi, violating rules such as "Two pawns can not occupy the same column" or "a piece can not be placed in a position where it is unable to move or promote" results in an immediate loss for the one who violated the rule. Thus, by placing a pawn in this location, the player automatically loses the game by violation of a rule. The checkmate that the player gives doesn't matter because it was obtained through the rule's violation.

In certain Shogi variations, such as yari shogi, a pawn can be used to give checkmate.

  • I find this explanation unsatisfactory because mating by dropping a lance is legal. However, the dropped lance has no more legal move than the dropped pawn in this situation. Too bad there is no link for this explanation found "on the web"... – Evargalo Mar 22 at 19:56

As I wrote the comment on @Rinzwind's posting, I had an idea allowing me to expand on the 'too easy' comment I made some time ago:

Perhaps mate can't be delivered by pawn drop, but not because it's is too easy, but because a pawn-in-hand is too easy to acquire. It removes the challenge from the game. It's really common to have a pawn or two in-hand. Even if I don't, I could almost certainly get one easily, by 'sacrificing' a bishop, rook, or perhaps a lance. Easy.

Say you have a pawn defended by a gold. If I need a pawn to give mate, I take the pawn with a rook. If you recapture, you're mated because I have a pawn in hand. Thus you must take some defensive move. Now I gobble the gold with the rook.

Perhaps the 'get a pawn any way you can' tactic was just too common.


One theory that I find reasonable is that the prohibition was originally unique to tsume problems, which makes them more fun, and later re-imported to normal shogi as well.

Another interesting one is a claim that it's implemented to prevent cheating of dropping the hidden 19th pawn to checkmate and immediately stir the pieces to blur it.


If this discussion is about 打ち歩詰め, one hypothesis is

Betray and kill the king by the lowest rank piece is forbidden when Sengoku Period(Japanese warring period).

And the other consideration is

Since there are 18 pawns altogether from both players, using them for winning spoils the nature of game Shogi.

  • Thank you for this answer ! I find both hypothesis interesting but not completely satisfying. If 1, why is it allowed to mate by advancing a pawn ? Maybe it doesn't count as betraying because the pawn comes openly ? If 2, we would need a specific description of the nature of shogi to appreciate why pawn-drop-mate spoils it... – Evargalo May 19 at 7:32

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