How Koga decides
- One of our pieces steps off a square, and a LATER move of ours puts a different friendly piece onto that very square.
- The vacated square must still be free when the second piece arrives — if the opponent dropped a piece there in between, we are merely recapturing, not exploiting a cleared square.
- The two moves must be made by two DIFFERENT pieces. A single piece shuffling out and back is just manoeuvring, not a clearance.
- One of our pieces steps off a square that was sitting on a line (rank, file, or diagonal). A later move sends one of our rooks, bishops, or queens sliding along that now-open line.
- The square that was vacated must lie between the slider's start and its destination — that is what proves the first move did the opening.
- We do not count a clearance unless the beneficiary move actually achieves something: it gives check or mate, promotes a pawn, or the piece that arrives then attacks an enemy piece.
- The beneficiary should USE the cleared square or line, not immediately cash it in with a capture. A capture on that square is better explained as winning material than as a relocation, so it does not qualify.
- If the engine's main line simply ends with our piece quietly settling on the cleared square, we trust that endpoint as the demonstrated payoff — Lichess often stops the line once the square is claimed.
- Two surviving shapes only: square and line. Looser ideas (a third 'support' pattern, and a single-move guess with no follow-up to confirm it) were dropped because they fired far too often by mistake.
- Clearance and a discovered attack often describe the same move from two angles: the piece that steps aside both vacates a square AND unmasks an attacker behind it.
- When a discovered attack is the primary motif — the unmasked attacker then strikes down the opened line, or the discovered attack is itself the headline of the move — we drop the clearance label as redundant and let the discovered attack stand alone.
Test positions (the examples that guard against regressions)
Line clearance with a quiet beneficiary
Lichess 00AhO. After ...Bb7, the bishop steps off c8 and opens the eighth rank between the rook on f8 and the white queen on a8. The beneficiary is the quiet ...Ra8, claiming the open line to win the queen — so it counts even though the rook move is not itself a capture or check.
Square clearance for a promotion
Lichess 00oYS. ...Rd1 steps the rook off c1, vacating that square. Two moves later the c-pawn promotes on the now-empty c1. The promotion is payoff enough on its own to confirm the clearance.
Square clearance settled at the end of the line
Lichess 01Aoh. After the bishop sacrifice on h7 and the king recapture, hxg5 clears h4 so the queen can occupy that square on the final move of the line. Even with no capture or check on that last move, the queen settling on h4 is the demonstrated point of the clearance.
Line clearance, not attraction
After Nxe5 the knight steps off f3 and opens the line for Qd1-h5. The queen on h5 then threatens the loose bishop on h3. (The queen also eyes the e5 recapturer along the fifth rank, but taking it would lose the queen, so the real idea is the cleared line — clearance, not attraction.)
Golden puzzles — every real Lichess puzzle Koga is tested against for this tactic (6)
Lichess 01hsz
Lichess 01hsz (rating 2070). Solution: Ne2+ Bxe2 Qa1#.
Lichess 06T6r
Lichess 06T6r (rating 1260). Solution: Qd2+ Qe2 Rg2+ Kxg2 Qxe2+.
Lichess 06k0H
Lichess 06k0H (rating 799). Solution: Nf7+ Rxf7 Rg8#.
Lichess 04KkX
Lichess 04KkX (rating 1948). Solution: Nf6+ gxf6 Qg4+ Bg7 Bxf6.
Lichess 02b7o
Lichess 02b7o (rating 1784). Solution: a4 Ke7 Ba3.
Lichess 03EVA
Lichess 03EVA (rating 1973). Solution: Nf4+ Bxf4 Qd5+ Kh2 Qxb3.