Sanrensei

Sanrensei refers to a powerful opening strategy in which a player places three stones on star points along one side of the board. It begins with a nirensei (two star points) and adds a third stone to form a big territorial and influence-oriented structure. 

Traditionally played by Black, it became iconic during the Shin Fuseki era in the 1930s and was largely abandoned with the advent of AI, which exposed its weaknesses.

This opening emphasizes influence and invites the opponent to reduce or invade. The Sanrensei player aims to use their resulting thickness to attack, rather than secure small territory early. Its success often hinges on effective use of moyo-building and whole-board balance.

The formation can be flexible: players may choose to attack, defend, or build based on how the opponent reacts. 

While AI programs today tend to favor territory over influence, the Sanrensei still finds use among amateurs and in specific high-level games where psychological pressure or familiarity with fighting is an advantage.

Explore more about this and other classic openings in the ‘Opening Classics’ lesson from The Main Principles of a Glorious Opening course.