Pawn Can Matter!

Logic Level pending

It's White's turn. Assuming optimal play, what is the minimum number of moves to win the game?

If you think the checkmate is impossible, select "None of the choices".

10 8 9 None of the choices

1 solution

Michael Huang
Jan 10, 2017

This is one of the famous endgame puzzle - Saavedra position .

Even though there may seem to be no winning position, if you push the pawn forward, you have the upper advantage. Then, the rook keeps checking your king until Kc2, which gives White the advantage to reverse the winning outcome.

For the queen promotion, this leads to the stalemate, so promoting to the rook is the right choice.

Here is one of the possibilities (since there is no way for the black rook to checkmate the king easily):

	White	Black
1.	c7	Rd6+
2.	Kb5	Rd5+
3.	Kb4	Rd4+
4.	Kb3	Rd3+
5.	Kc2	Rd4
6.	c8=R!	Ra4
7.	Kb3	Rg4
8.	Rc1#

It's hard to see a mate in 8 ahead with optimal play.

A Former Brilliant Member - 4 years, 5 months ago

Can't black play something other than Rd6+ on the first move, that might change the optimal play (assuming survival for a longer game).

Siva Bathula - 4 years, 5 months ago

Like rook watching the King on the other side? I don't think that long survival works. If this is so, then this does not minimize the number of moves. This increases the move count.

So to avoid the controversy, assume that both players do not repeat the same moves.

Michael Huang - 4 years, 5 months ago

Black will always do his best to survive for long, that is the easiest trick of all, hence his optimal play in the given position, the mate is not straight forward takes a lot of manouevring and hence 8 is the least for worst play by black and best play by white.

Siva Bathula - 4 years, 5 months ago

@Siva Bathula – The first move shows that the Black has to prevent the White from queening. If Black does not make that move, then this forces the White to promote the pawn, which violates the condition that both players play optimally. In addition, since the king is allowed to move an adjacent unit, it is not possible to create different patterns from the solution indicated.

The puzzle may not be easy as you might think, assuming the mate is impossible. But moving the pawn forward turns the outcome. Try moving different pieces and see if you can come up with a different idea.

Michael Huang - 4 years, 5 months ago

@Michael Huang – https://en.wikipedia.org/wiki/Saavedra_position According to this wiki article, black can offer longer resistance.

Siva Bathula - 4 years, 5 months ago

@Siva Bathula – Yes. You made the point right here. :) However, I don't think that is the minimum moves. Moving Kb3 is erroneous for few reasons:

1) This forces the rook to check from another side. 2) There is still opening spaces for the Black king to move.

Nice idea you share though! :)

Michael Huang - 4 years, 5 months ago

@Michael Huang – So 8 may not be the optimal answer? It can be much longer than that?

Siva Bathula - 4 years, 5 months ago

@Siva Bathula – If you read the previous comment, you notice that Kb3 wouldn't be possible.

Michael Huang - 4 years, 5 months ago

@Michael Huang – I think kb3 may not be needed at all. The black king can move between kc1 and kb2 with the rook acting as a block to the white queen and also to check the white king, eventually forcing the white king to move towards the black king and white queen to attack through farther squares.

Siva Bathula - 4 years, 5 months ago

@Michael Huang why does black follow king until the end instead of following it for two moves and then killing the pawn?

Elias Lageder - 4 years, 4 months ago

assuming optimal play rook would put pawn as first priority to prevent chances of checkmate before going for the king

NSCS 747 - 11 months ago