Finding the Key Move in Tsume Shogi: Tries, Red Herrings, and Variations

A tsume shogi problem has exactly one correct first move — chess-problem solvers call it the 'key' (every problem on TsumeDojo is verified to have a unique first move and the shortest mate length). The trouble is that the board usually offers several checks that look like they mate but don't: these are 'tries', or red herrings. Solving means rejecting the tries to find the one key, then reading the defender's variations through to the best defense. If you have solved 'mate in N' chess problems, this is the same hunt.

Tries (red herrings) — checks that look like mate but fail

In most positions there are several ways to give check, and most of them are tries: they look strong, but the defender has one best reply that escapes. For each candidate first move, ask whether the defender's best response avoids mate — if it does, that move is a try, not the key. The key is the single first move that mates against every defense. Don't grab the first check that 'looks like mate'; confirm there is no escape first.

Reading the variations — the defender plays the best defense

Once you pick a first move, list every reply the defender has — running the king, capturing the checking piece, or interposing — and confirm you have a mate against each one. A single escape means the move is wrong. By convention the defender plays the longest-resisting best defense (see the rules article), so do not settle for reading only the convenient reply. You have found the answer only when you have read out the most stubborn variation to mate.

Narrowing the candidates

Rather than reading every check at random, narrow the field first: (1) count the king's escape squares and prefer checks that take them away; (2) deprioritize checks where your checking piece is simply captured, since they rarely continue; (3) work backward from a mating shape you know (such as a gold in front of the king) and look for the first move that leads into it. Reduce the candidates to a few, then read the variations on those.

Cooks (yozume) and the unique key

A well-made tsume has a unique key. If two different first moves both mate, the problem is 'cooked' (Japanese: yozume) — considered a flaw. Every problem on TsumeDojo is solver-checked to have a unique first move and the shortest mate length, so you can trust there is exactly one key and confidently reject the tries. Even when several first moves look like they mate, only one is the shortest, sound answer.

How to practice

On problems with some length, don't play the first plausible check — weigh a few candidate first moves and ask 'is this just a try?' before committing, then read the most stubborn variation to mate. Training your eye to spot the key and dismiss the red herrings carries straight over to the accuracy you need in real endgames. Work up through the move-count levels on TsumeDojo to sharpen it.