Completely forced checkmates

This is so awesome and satisfying, thanks for sharing!

Bump

Since the first position works as a selfmate problem, where one side forces the other to give mate (against their will), I initially thought you were just making examples of that unconventional genre. But looking at the other positions and reading your definition of the task more carefully, I realised you're aiming for something different: after the initial move, both sides must play their only legal moves which eventually result in a forced mate.

Thus in the third problem, if this were a selfmate, then an alternative solution would be 1.Ng7+ Qe6/Bf5 2.Qc6+ forcing 2...Kxc6 mate. But 2.Qc6+ is not White's only legal move and so it doesn't satisfy your original goal. Hence your intended solution is indeed unique. Nice job!

I don't believe the task you're proposing has a name in the chess composition field. The way it restricts play on both sides probably makes it unlikely to work as a proper genre, compared with something like selfmates which enable countless ideas to be shown. Still, it's an interesting construction task idea.

How did you come up with these? Just playing around?

Is there an error above? Pretty sure black's bishop can go anywhere on that long diagonal. On the other hand, I am pretty sure that Bc6 is a solution.

Wrong on all three points.

To address the last point first, no, if White plays Bc6 Black will capture it, and White is then forced to retreat his Rook to g2 to block the check... after which there is no more pin on the back rank and Black can simply move his b8-Bishop and THERE IS NO MATE.

Bear in mind the conditions: White is trying to force Black to mate White.

Oh oops my bad...forgot that the rook can retreat sorry lol.

I'll post the solution in invisible ink, just highlight it with your mouse to read it.

White's Rook must stay on the 8th rank in order to keep the b8-Bishop pinned. As long as that pin is maintained, the ONLY piece that Black can move is the b7-Bishop... and it is line-pinned and can only shuffle back and forth along the long diagonal.

So the self-mate pattern depends on forcing Black to play B(from b7)xB(on c6) mate. But it will only be mate if the White Rook is unable to recapture the Bishop or block the check.

So if the two Bishops are adjacent (zero squares between them), the White Rook MUST sit on h8. No other square will be mate (c8 instead allows a recapture while d8, e8, f8 or g8 allows a block).

If there is ONE square seperating the Bishops, the closest the White Bishop can get is d5 (not c6), and White Rook MUST be on c8. That's because c8 is the only square (other than h8, which is required for the zero-squares-apart coordination) that allows no blocks or recaptures.

If there are TWO squares between the Bishops, the closest the White Bishop can get is e4, and the White Rook MUST sit on d8.

... and so on. 

See if you can figure it out now.

Hmm

That’s quite a setup, but most of the moves aren’t forced. When black isn’t in check, they can shuffle the bishop back and forth instead of playing the moves you showed. White could also take the bishop with the king.

edit: somehow just saw your second post, if that’s how it’s “forced” then it’s really just the best moves lead to mate in that position

Gut gespielt

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blueemu, a short solution is possible. 1. Rh8 Bc6. 2. Bd5 Bb7. 3. Bc6 Bxc6.

The puzzle is correct. I know this is hard to accept, but it is.

White's 1. Rh8 throws away the "win", and is met by Bf3 and White is in ZUGZWANG.

Call each square on Black's back rank by a number.

h8 is zero. If there are ever ZERO squares between the Bishops then the White Rook must immediately play to h8,

c8 is one. If there are ever ONE square between the Bishops, then the White Rook must immediately play to c8.

d8 is two. If there are ever TWO squares between the Bishops, then the White Rook must immediately play to d8.

e8 is three. If there are ever THREE squares between the Bishops, then the White Rook must immediately play to e8.

f8 is four. If there are ever FOUR squares between the Bishops, then the White Rook must immediately play to f8.

The above rules (which back-rank squares coordinate with which distances between the Bishops) only apply when Black moves his Bishop CLOSER. If he retreats it (moving it further away), then White should follow with his own Bishop, maintaining the distance.

Some examples:

What isn't true?

Let's try it!

I play 1. Rf8

Rh8

You retreat, I follow, keeping the Bishops touching.

Correct. The puzzle is sound. You just need to realize which square the Rook must play to depending on how far apart the Bishops are.