The Castle

The castle is a fortress-like formation of pawns and pieces built around one's own king in closed structures — so solidly that the attack on the other wing can be conducted without fear. Erecting it is the easy part; knowing when the gates may be opened is the art. The games, from the great Candidates tournaments, show both the construction and the release of the pieces.

White themselves are planning b3-b4 after proper preparation. Now after ... White will have ... , and on -