In chess, the fianchetto (English: /ˌfiənˈkɛtoʊ/ or /ˌfiənˈtʃɛtoʊ/;[1] Italian: [fjaŋˈketto] "little flank") is a pattern of development wherein a bishop is developed to the second rank of the adjacent b- or g-file, the knight pawn having been moved one or two squares forward.
A long fianchetto on the kingside is more rarely played, because it weakens the pawn shield in front of the castled position and controls a less important square.
Black often plays ...Ba6 in the French Defence, and in the Queen's Indian Defence if White plays g3 in order to fianchetto his own bishop (Aron Nimzowitsch's move against the classical main line).
The game Rubinstein–Nimzowitsch, Marienbad 1925,[3] had four fianchettoed bishops, two developed knights, and two on their home squares.
In this position, Nimzowitsch humorously pointed out in My System: "Each side castles now with a clear conscience, for not even the most hypermodern pair of masters can produce more than four fianchettoed Bishops!