Keshi

Reduction (Keshi) is a fundamental strategic concept in Go, referring to the act of reducing an opponent’s territorial framework without committing to an all-out invasion. Unlike an invasion, which seeks to establish a living group inside the opponent’s territory, keshi operates by limiting their potential and forcing them to settle for less.

When to Reduce:

• When an opponent’s framework is solidified and it is too risky to invade.
• As an alternative to invasion when maintaining stability is preferable.

Reduction vs. Invasion

Aspect	Reduction	Invasion
Objective	Limits opponent’s potential	Aims to establish a group
Risk Level	Low to moderate	High (in most cases)
Typical Use	Midgame, when frameworks form	Midgame or late opening
Effect	Weakens opponent’s moyo	Creates direct conflict

Keshi has been a crucial concept in professional Go throughout history, especially in influence-based games where players aim to balance territory and power. In contemporary play, reducing large moyos efficiently is often necessary to compete against territorial frameworks created through modern AI-inspired openings.

If you want to know more about reductions, explore the “Reducing Is Good Enough!” lesson in our Fearless Invasions course.