Identify a problem where a potentially winning move draws because of the 50 move rule I'm trying to recall a particular chess problem. It's related to retrograde analysis. All what I can remember is this: it's an endgame where there is only one way to reach the position, and during last 49 moves there were no captures, so a potential winning move draws instead.
There are dozens of problems that illustrate a potential winning moves that instead leads to a draw because of the 50 move rule.

One example is the following mate in four published by Léon Loewenton in 1956 :

[fen "5KBN/p2ppp1r/1p4pp/b7/RP6/1PP4P/1RpPPPkP/n1B1Q1N1 w - - 0 1"]

1. Nf3 Rg7! 2. Kxg7! (2. Qg1+?? draws)


There is an apparent mate in three moves: 1. Nf3 followed by 2. Qg1(+) and 3. Qg3 mate. 

However, after 1. Nf3 Rg7! 2. Qg1+ black claims a draw according to the 50 moves rule (the retrograde analysis is left as an exercise to the reader!).

If white plays 2. Kxg7!, the capture breaks the 50 move chain and white can mate with 3. Qg1(+) followed by 4. Qg3 mate.