Beat caveatcanis

In the following position (from my most recent OTB tournament) I have just blundered by moving my bishop from e6 to f7. (I should have put the bishop on d7.)

So: White to play and win!

And why can't black play 4. ... Rd8?

4. ... Rd8 is answered by 5. Qe5+ Kg8 6. Qg7#

That's true, but I'm not sure that 5. Rxa8 actually wins

Lets play a forum game from that position. You play black.

Okay, you and caveatcanis play black.

My move is 5. ... Kf7

I realise that, and we're trying to prove whether white wins or not with that.

Your move (I played your only move).

5. Rxa8+ actually forces mate in 10.

I checked the position with my computer before posting, but decided that expecting people to find the mate would make the problem too hard.

How?

One line is:

5.Rxa8+ Kf7 6.Qe8+ Kf6 7.Qh8+ Kf5 8.Qc8+ Ke4 9.Qxg4+ Ke5 10.Qe2+ Kf6 11.Re8 Be7 12.Qxe7+ Kf5 13.Qg5#

but there are many side-variations.

And I play 7. ... Qf6

Presumably you meant Qe6?

Ra6 looks pretty clean but even Qxc5 is safe because it covers g1, stopping back rank mates. Even Qxe6 is enough.

Really great problem !! And I liked that you took it from one of your own games !!

Seems legit. Did you use a computer to check every move? Because the position is really quite complex and tends to result in unexpected "better" winning moves.

Yes - I computer-check positions before I post them, because I don't want to waste anyone's time.

On the other hand, my comments on other people's positions are rarely checked, which is why they're often wrong.

Ah ok thanks for the effort. Quite an interesting position to analyse, and absolutely horrible to verify by hand :).