Positions in which only a single long sequence of correct moves avoids forced checkmate sequences So for n steps, one player can only choose one out of many moves, because all others lead to forced checkmate sequences. Only one path from the root to the leaves of the game tree avoids a certain loss.
Does this concept have a name? Are there any known positions where this is the case?
To start off, with such a requirement, the sequence would have to end in a draw. Well, more than most likely that is.
There is a similar concept from another question called the &quot;Nunn Convention.&quot; It is a term to describe a move by one side that is the only way to draw, with the extra requirement that it isn't the only legal move. That extra requirement is what makes it &quot;Nunn.&quot; It isn't quite what you wish for, but it is close.
The Matplus.net thread from which I learned the concept contains the below example. It is the record length of 32 plies for such a &quot;Nunn&quot; sequence. It is from post number 19.
[Title &quot;Geir Sune Tallaksen Østmoe, Matplus.net Forum 8/9/2019, White To Draw&quot;]
[FEN &quot;k1B5/r1p1p2b/nPPP2R1/BN2b1R1/2P2qp1/p7/P3P2P/6Kn w - - 0 1&quot;]

1. Bb7+ Rxb7 2. Rg8+ Bxg8 3. Rxg8+ Nb8 4. Rxb8+ Kxb8 5. bxc7+ Rxc7 6. dxc7+ Bxc7  7. Bxc7+ Qxc7 8. Nxc7 Kxc7 9. Kxh1 Kxc6 10. Kg2 Kc5 11. Kg3 Kxc4 12. Kxg4 Kc3  13. h4 Kb2 14. h5 Kxa2 15. h6 Kb1 16. h7 a2