Mate in 3 — Problem #1
Black to move — find the mate
☖
9
8
7
6
5
4
3
2
1
一
二
三
四
五
六
七
八
九
☗
Show solution
▲１二歩 △同 玉 ▲１三香
Why this move works
The answer is ▲１二歩 △同玉 ▲１三香. The key is a pawn sacrifice that removes the defender’s blocking option: if you immediately play ▲１三香, the defender (who has many pieces in hand) simply drops a piece on 1二 to block the lance.
So first play ▲１二歩. The gold on 3二 covers 2一 and 2二, so the king cannot flee and must capture: △同玉. Now that the king has been pulled to 1二, ▲１三香 checks from right next to it — there is no gap left to interpose a blocker, and the lance is protected by the gold on 1四. Erasing the defense with a tiny pawn sacrifice is the whole point.