Release the position

Release the position (Retract moves until you get a position which is obviously legal).

I think I will pass

Originally posted by David113
[fen]bk1q1nQ1/brppKppp/1p2p3/8/8/P7/1PPPPPPP/5B2[/fen]

Release the position (Retract moves until you get a position which is obviously legal).

well, move Kf7 and it's legal. But I know what you mean - too hard!!

Originally posted by David113
[fen]bk1q1nQ1/brppKppp/1p2p3/8/8/P7/1PPPPPPP/5B2 w[/fen]

Release the position (Retract moves until you get a position which is obviously legal).

2wR and wB were captured behind their own pawn wall. Ba7 is not promoted - wP\'s prevent a promoted dark-square B from leaving the first rank. It must go home before ...e7 is retracted. 1...Qc8xNd8?? leaves no way to ever unlock the NW corner.

So, how to shield the 8th rank for wK? Only a bNd8 can possibly work, and it must come from c6. However, an N of either color cannot retract directly to c6, which would have one of the K\'s in check with checking side to move.

The only answer is to add a non-N piece to the mix, outside the bP and wP walls, and use it to deliver an N on c6 legally.

White needs to uncapture a bNg8 right away to give Black some moves, which makes 3 bN\'s needed, so one is promoted. A promotion requires at least two captures by the a-pawn, one of which must be a wN. White must therefore wait until this wN is back on the board, so it can uncapture the non-N, which uncaptures yet another wN on c6, which uncaptures a bNc6.

Retract 1...Qc8 2.Qh8xNg8 Nf6 3.Qg8 Ne4 4.Qh8 Nc5 5.Qg8 Nb3 6.Qh8 Na1 7.Qg8 N=a2 8.Qh8 b3xR 9.~ a4xN 10.Nd4xRb3 Rc3 11.~ Rc6 12.~ RxNc6 13.NxNc6 Nd8 etc.


With wK freed, the position unwinds easily.

Originally posted by SwissGambit
2wR and wB were captured behind their own pawn wall. Ba7 is not promoted - wP\'s prevent a promoted dark-square B from leaving the first rank. It must go home before ...e7 is retracted. 1...Qc8xNd8?? leaves no way to ever unlock the NW corner.

So, how to shield the 8th rank for wK? Only a bNd8 can possibly work, and it must come from c6. However, an N ...[text shortened]... ppKppp/1p2p3/4N3/p7/P1r5/1PPPPPPP/R4BN1[/fen]
With wK freed, the position unwinds easily.

Very nice 🙂

The problem with the position is that The White king cannot reach e7 without passing though check.
This position cannot be reached without having at least one black pawn off the 7-th rank (g or c)

Originally posted by preachingforjesus
The problem with the position is that The White king cannot reach e7 without passing though check.
This position cannot be reached without having at least one black pawn off the 7-th rank (g or c)

No, you don't need g- or c- to move. The b-pawn is off the 7th rank. wK entered at a6.

doesn't make sense to me....

please post a move list for a game that ends in this position.

Originally posted by preachingforjesus
doesn\'t make sense to me....

please post a move list for a game that ends in this position.

Let\'s not take the lazy way out just yet. Imagine that only wK and the black Pawn structure are on the board. Isn\'t it obvious wK can just play Kb5-a6-b7-c8 etc.?

You have currently demonstrated the first step.

what you have not done is to demonstrate that after black has extracted his pieces from the back rank that white can actually take this path.

and then you need to demonstrate that black can move his pieces to their current location.

The key was actually pretty simple.

The black-suared bishop sceens the white king from check until the Knights get into place.

here is the mave list:

1. Nc3 Nf6 2. Nb1 Nh5 3. Nc3 Ng3 4. Nb1 Nxh1 5. Nc3 Ng3 6. Nb1 Ne4 7. Nc3 Nc5 8. Nb1 Nb3 9. a3 Nxc1 10. Nc3 Nb3 11. Qb1 Nd4 12. Qa2 a5 13. Kd1 Ra6 14. Kc1 Rh6 15. Kb1 e6 16. Qd5 Bc5 17. Ka2 Qg5 18. Kb1 Nbc6 19. Ka2 Ke7 20. Kb1 Ba7 21. Ka2 b6 22. Kb1 Ba6 23. Ka2 Ra8 24. Kb1 Nf5 25. Ka2 Nh4 26. Kb1 Kd8 27. Ka2 Ng6 28. Kb1 Kc8 29. Ka2 Nd8 30. Qd6 Kb7 31. Qf8 Kc6 32. Qh8 Nf8 33. Kb3 Bd3 34. Ka4 Bg6 35. Qg8 Kd6 36. Qh8 Qf6 37. Kb5 Nc6 38. Ka6 Ne5 39. Kb7 Bb8 40. Kc8 Qf4 41. Kd8 Nc6+ 42. Ke8 Nd8 43. Qg8 Ra6 44. Qh8 Be4 45. Qg8 Ba8 46. Qh8 Qe4 47. Nd5 Rh3 48. Nf4 Rc3 49. Nd3 Qb7 50. Qg8 Qc8 51. Qh8 Kc6 52. Qg8 Kb5
*


this is as close as I can get it to your second diagram

Originally posted by preachingforjesus
You have currently demonstrated the first step.

what you have not done is to demonstrate that after black has extracted his pieces from the back rank that white can actually take this path.

and then you need to demonstrate that black can move his pieces to their current location.

I stopped where an experienced retro solver would usually stop. It\'s obvious to me that it\'s legal, but you\'re new to these, so I\'ll humor you.


0... Qc8-d8 -1. Qh8xNg8 Nf6-g8 -2. Qg8-h8 Ne4-f6 -3. Qh8-g8 Nc5-e4 -4. Qg8-h8
Nb3-c5 -5. Qh8-g8 Na1-b3 -6. Qg8-h8 a2-a1=N -7. Qh8-g8 b3xRa2 -8. Ra1-a2
a4xNb3 -9. Nd4xRb3 Rc3-b3 -10. Nf3-d4 Rc6-c3 -11. Ng1-f3 Rc3xNc6 -12. Nb4xNc6
Nd8-c6 -13. Ke8-e7 Ng6-f8 -14. Qf8-h8 Nf4-g6 -15. Qe7-f8 Nd3-f4 -16. Kf8-e8
Nf4-d3 -17. Qe8-e7 Nc6-d8 -18. Nf3-g1 Qd8-c8 -19. Ng1-f3 Kc8-b8 -20. Nf3-g1
Rb8-b7 -21. Ng1-f3 Kb7-c8 -22. Nd3-b4 Ka6-b7 -23. Nc1-d3 Kb5-a6 -24. Na2-c1
Qg5-d8 -25. Kg8-f8 Nd4-c6 -26. Kf8-g8 Bf3-a8 -27. Kg8-f8 Ra8-b8 -28. Kf8-g8
Bb8-a7 -29. Kg8-f8 Ra5-a8 -30. Kf8-g8 Kc4-b5 -31. Kg8-f8 Rf5-a5 -32. Qe7-e8
Qg4-g5 -33. Kf8-g8 Qg5-g4 -34. Ke8-f8 Qg4-g5 -35. Kd8-e8 Qg5-g4 -36. Kc8-d8
Qg4-g5 -37. Kb7-c8 Nd5-f4 -38. Ka6-b7 Kc5-c4 -39. Qe8-e7 Kd6-c5 -40. Kb5-a6
Nc6-d4