[Event "Le verrou"] [Site "https://lichess.org/study/xOVSnWLR/9R8q59cW"] [Date "????.??.??"] [Result "*"] [Variant "From Position"] [ECO "?"] [Opening "?"] [Annotator "https://lichess.org/@/michel_PR"] [FEN "r1b2rk1/2p1q1n1/ppPp1b1p/3Pppn1/1P5B/2N3P1/P2NB2P/2RQ1R1K w - - 0 1"] [SetUp "1"] [Source "https://lichess.org/study/xOVSnWLR/9R8q59cW"] [Orientation "white"] 1. a4! { Les Noirs n'ont plus la possibilité d'ouvrir la colonne "a" } *