The question concerns chess. I call a move *forced* if, in a given position, is the unique move consistent with the rules of the game. I wonder what is the largest integer $n$ such that there exists a legal position in which:

both black and white have forced moves for $n$ consecutive times;

the position is never repeated (with the same color having to move).

Notice that without condition 2., the answer is $\infty$.

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