What is the longest non-cyclic forced sequence of moves? [duplicate]

I am looking for positions from where every move is forced up to a certain depth. If the original position (or one in between) occurs again, the sequence is finished there.

• Do you mean that every move of both players is forced or of just one player? (In the first case, mates in N moves are out of the question, because the moves of the losing side are not forced as his decision makes no difference.)
– JiK
Commented Apr 3, 2014 at 13:41
• Yes, it's about forced sequences for both players. It doesn't need to end in checkmate, the only requirement is that there is just one possible move for each player for a long time. Commented Apr 3, 2014 at 16:00
• I think it eas not intended by the one asking the other question but it is trivial to construct a position that is forced to repeat again and again, making that sequence infinite. Commented Apr 3, 2014 at 20:49

9 moves

You mean like this?

``````[Title "Vilhelm Röpke, Skakbladet 1942, Mate In 6"]
[FEN "K1k5/P1Pp4/1p1P4/8/p7/P2P4/8/8 w - - 0 1"]
``````

White mates in 6.

I guess that's 9 consecutive forced moves. It would be eleven except for black's choice of promotion piece on his fifth move. I don't know if it's a record, and I don't know who composed this classic chess problem.

• I miss understood what the OP was asking, I end up deleting my answer and upvoting yours since it goes straight to the point. Commented May 21, 2014 at 13:43
• Can c1=Q be considered forced? I mean surely I had C1=N, C1=B, C1=R
– Alan
Commented May 21, 2014 at 18:32
• @Alan It's not counted in the 9 half-moves for that reason. ("It would be eleven except for black's choice of promotion..."). Commented Jun 12, 2014 at 10:32