How can you deliver checkmate with a king?

It's an achievement where the king moving results in mate.

Occasionally people are confused about the identity of the piece delivering a checkmate. It's not the piece attacking the king but the piece that was moved last to get into the checkmate position. These two are often the same but not in a discovered checkmate!

Thanks to you all! :blush

Reveal a checkmate by moving your kin. DONE

Checkmatex

I think it Looks like this

Or this :

(castling counts as a kings move).

this

Didn't you overlook another mate?

h2# is also checkmate

It's not possible. As shown moving the king reveals the checkmating piece. It's always a discovered check.

A king cannot "deliver" checkmate because that would be against the rules. But it can reveal the piece that does. The delivering checkmate piece is the one that, on the next move, would capture the opponent's king. A king can never do that.

The pawn moves and the black king is checkmated. But it's not the pawn that checkmates because the pawn cannot capture the black king on the next move. The way a discovered check was described to me (in this case would be) the pawn is the trigger, the bishop is the bullet.

You're wrong. The pawn checkmates as it is the last unit that plays. Checkmate is not a relationship between an attacker and a king but an overall state on the board where the king attack is just a contributing factor. Checkmate also demands control of all squares around the king including selfblocks by pieces of the king's own color. This was discussed extensively only a few months ago on these same forums.

You could be right. I was just going by the definition of "deliver". The definition I was using, in Merriam Webster, is "to send (something aimed or guided) to an intended target or destination."

Certainly the pawn is not aimed at or targeting the destination (the king). Only the bishop is doing that. The pawn just gets out of the way of the deliverer.

Yes checkmate is an overall position on the board, with certain conditions all applying. But in all cases of checkmate, an attacking piece would capture the king if it were possible to pass or forfeit the next move. That attacking piece is the deliverer of checkmate.

Um... The red king is in checkmate/check before the white king could move, so that scenario is impossible

In a sense the issue was decided long ago (don't know how long) in the composition domain. "Checkmate" is part of the chess rules but the "identity of the checkmate deliverer" is not. But it is a necessary part of the composition vocabulary in the definition of composition tasks. Many composition tourneys have specific requirements for the content to be shown. Example: construct a #3 problem with as many different king check or checkmate moves as you can . accomplish. Or, construct a helpmate where every unit type (K,Q,R,B,N,pawn) delivers a checkmate in some variation. Note that the delivery question plays for all unit types, not just the king.

Of specific interest are the "double checkmates" where both units deliver check in the checkmate position. Which one delivers the checkmate in your system? Do you now rush in to hand some extra bonus points to the last playing unit?

And perhaps the hardest question to answer is about stalemate. Which unit delivers stalemate? None at all? All of them? Whatever your choice it demands yet another definition for "delivery". How much simpler to stick with the "last played unit" as we do in composititions!

Actually you can make a stronger case for the delivery of "check" where commonly only one unit attacks the king and the overall position doesn't matter. But the composition field still sticks with the "last unit played" for consistency. And to avoid identifying the nasty double check deliveries.