Destroying detection

Destroying means sacrificing a piece to capture a pawn that shields the enemy king, tearing open the king's cover so the rest of our pieces can attack. Koga flags the capture, the shield pawn it removes, and the exposed king.

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How Koga decides

Definition Destroying the pawn shield
  • We capture a pawn that is shielding the enemy king, giving up a piece worth more than the pawn we take.
  • The point is not the pawn itself — it is to tear a hole in the wall of pawns in front of the king so our other pieces can pour in.
  • The classic shape is the Greek gift: a bishop or knight crashes into f7/h7 (or the queenside equivalent) right next to the uncastled or castled king.
Geometry Where the capture must land
  • The captured pawn must sit on a shield square: one of the two ranks directly in front of the enemy king's back rank.
  • It must also be close to the king — on the king's file or one of the two files beside it.
  • Squares like f7, g7, h7 (or a7, b7, c7) for a black king on the back rank are the typical targets.
Conditions What makes it a sacrifice
  • The move must be a capture, and the capturing piece must be worth strictly MORE than the pawn it takes — we are deliberately giving up material to open the king.
  • There must be at least one OTHER friendly piece (knight, bishop, rook, or queen) still on the board to exploit the exposed king. A lone sacrificer with no follow-up support is not flagged.
  • We judge only the geometry, the material given up, and the presence of a follow-up piece — we do not separately prove the sacrifice is objectively sound.
Filters When we stay quiet
  • If the move is a fuller king-hunt sacrifice that we already recognise as Bombardinio, that label takes over and Destroying is suppressed so the same idea is not reported twice.

Test positions (the examples that guard against regressions)

Knight crashes into f7

From the game kwGLefOd. White plays Nxf7, giving up the knight to rip open the black king's f7 shield. The knight is worth more than the pawn it takes, the black king sits right beside f7, and other white pieces remain to exploit the open king — so Koga calls this a destroying sacrifice. The geometric fork on the same move is demoted, because the king simply takes the undefended knight for free.

✓ detectedSacrifice on f7test_fork_demoted_when_king_recaptures_forker_in_kwGLefOd
r . . q k b . r
. b . n . p p p
p . . . p n . .
. p p . N . . .
. . . . . . . .
. . . . . N P .
P P Q P P P B P
R . B . . R K .
Sacrificed piece
Targeted / won piece
King

Greek gift on f7

A constructed Greek-gift position. The bishop captures on f7, giving up the bishop for a single pawn to shatter the shield in front of the black king on e8. With other white pieces ready to join the attack, Koga flags the destroying sacrifice.

✓ detectedGreek gifttest_detects_promotion_to_queen_as_destroying_on_f7
r n b q k . . r
p p p p . p p p
. . . . p n . .
. . . . . . . .
. b B . P . . .
. . . . . N . .
P P P P . P P P
R N B Q K . . R
Sacrificed piece
Targeted / won piece
King