A pawn on the second rank of the side to move, attacked by an opponent's piece, and either undefended or defended by at least one piece.

By Climbchess Research · 2026-05-08 · 3 min read · Updated May 8, 2026

SAE concept sae_7377 fires when a pawn on the second rank of the side to move, attacked by an opponent's piece, and either undefended or defended by at least one piece.. It appears in 1 of 9,950 Climbchess puzzles (0.0%), spanning ELO 2683–2683 (median 2683).

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This page documents A pawn on the second rank of the side to move…, one of 4,505 interpretable chess concepts extracted from Leela Chess Zero via sparse autoencoders. The full feature description from our SAE labelling pipeline reads:

A pawn on the second rank of the side to move, attacked by an opponent's piece, and either undefended or defended by at least one piece.

This pattern fires in 1 of our 9,950 tagged puzzles. The puzzles where it appears span ELO 2683 to 2683, with a median rating of 2683. That distribution tells you whether this is a beginner cue or a master-level subtlety.

Pattern statistics

Related concepts

The five concepts most often co-firing alongside this one (Jaccard similarity over the puzzle co-occurrence graph) are:

• A critical passed pawn or promotion threat in a complex endgame, often with… — similarity 0.100
• Passed pawn endgame with king opposition and advanced pawns racing to promote. — similarity 0.005
• Detects an empty square on the first rank that is attacked by a pawn and… — similarity 0.004
• A pawn (either colour) on the 2nd rank near the kingside, in a position… — similarity 0.002
• Active rook delivering or threatening a decisive mating attack in the endgame… — similarity 0.002

Example puzzles

Below are 1 puzzles spanning the rating distribution. Each links to its own page with full move list and related concepts.

• Puzzle zEqHG_M — ELO 2683, themes: advantage, deflection, endgame, side to move: White

How to use this page

If you want to train this pattern, open the Climbchess trainer and filter for puzzles tagged with this concept. The trainer surfaces them at the right difficulty for your current rating, and tracks how often you spot the cue versus miss it. You can also browse the related concepts above to see neighbouring ideas in feature space.

Climbchess concepts are not heuristics written by a human author. Each one corresponds to a single direction in the residual stream of Leela Chess Zero that activates on a specific board feature, then was labelled by reading the top-activating positions. This makes the catalogue exhaustive (every Leela-detectable pattern is in here somewhere) and falsifiable (you can replay our extraction).