Pandolfini's Puzzler #5 - The Missing Knights

ChessKids: Have you ever heard your parents talk about clothing being "retro"? It means "in the past." Well today we have a "retrograde" problem - you have to think into the past instead of into the future!

“This position may or may not have happened in a real game.” 

Question: “Whether or not it really happened, can you demonstrate how this position could legally occur in four moves (four for White and four for Black)?”

Zephyr was at first stymied by this one. But after trying out a few ideas, she was suddenly consumed by a glowing smile, and the Professor knew she had the answer. 

Did Zephyr find that the position was possible?

Zephyr found several variations leading to the position of the diagram. One variation is 1. Nf3 Nf6 2. Ne5 d5 3. Nc6 Nfd7 4. Nxb8 Nxb8. Another variation is 1. Nf3 d5 2. Nd4 Nf6 3. Nc6 Nfd7 4. Nxb8 Nxb8.

When the same position occurs by a different move order (or sometimes by different moves altogether) it’s called a transposition. Furthermore, the player creating the transposition has transposed moves.

Transposing moves can be a sophisticated way of tricking an opponent. By playing moves out of sequence, a player may be able to achieve the same setup, but in a way that prevents the opponent from doing something important. Bobby Fischer was famous for his clever transpositions.

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