[Event "Pattern Juggling: Endgame block and lune"] [Site "https://lichess.org/study/uZFAS28p/4tT8tOjo"] [Result "*"] [Variant "Atomic"] [ECO "?"] [Opening "?"] [Annotator "https://lichess.org/@/Illion"] [FEN "8/8/8/pp6/8/1P5k/P6P/7K w - - 0 1"] [SetUp "1"] [UTCDate "2017.08.25"] [UTCTime "21:00:30"] [Source "https://lichess.org/study/uZFAS28p/4tT8tOjo"] [Orientation "white"] { White is winning in this position, but must not allow black to exchange off the queenside pawns, or else be left with a drawn connected king KQ v K endgame. The correct move can be found here with some calculation, but a grasp of the "block" and "lune" pawn microstructures will quickly lead to the right answer with very little thought. } 1. a3 $7 { White sets up a "block", two pawns adjacent to each other. White can block the black pawns without exchanging. Regardless of which pawn black leads with, white -pushes past- with the other. The block keeps files closed and keeps pawns on the board. Here this structure will preserve both pairs of pawns on the board, and white can win by queening the h-pawn. } { [%csl Ga3,Gb3][%cal Ba3a4,Bb5b4,Ra5a4,Rb3b4] } (1. Kg1? b4 $7 { Black sets up a "lune", where white and black's pawns form a crescent or lune shape. The lune allows one to force the exchange of a pair of pawns, leaving the remaining pawns either both passed or both exchanged. This is exactly what black wants here, where passed pawns mean black promotes first and wins, while exchanging both pairs of pawns is a connected king KQ v K draw. } { [%csl Ga5,Gb4,Gb3,Ga2] } 2. a4 (2. Kf1 a4 3. Ke1 axb3 4. Kd1 b3 5. axb3 $10) 2... bxa3 3. Kf1 a4 4. bxa4 Kg2 $10) (1. a4 bxa4 $10) (1. b4 axb4 $10) 1... b4 (1... a4 2. b4 $18) 2. a4 $18 { White wins. } *