Throw-In in Go — How Hōrikomi Sacrifices Work | PlayGo.gg

A position where you sacrifice a stone to take away an eye and create a false eye.

What is a throw-in?

A throw-in is a single stone played onto a point the opponent will capture next move. On the surface it looks like a wasted move — the stone has only one liberty and is removed at once. The point of the technique is what changes during that brief life: the captured stone leaves behind a configuration that's now weaker — fewer liberties, a false eye instead of a real one, or a stone primed for snapback.

The arithmetic is simple. You give up one prisoner, but you destroy a much larger result: a living group becomes dead, or a one-eye shape loses its second eye. The Japanese name hōrikomi literally means "throwing in." Korean uses 사석 (sacrificed stone) for the broader concept and 던짐수 ("thrown move") for this specific tactic.

When to use a throw-in?

Four classic uses:

- Eye destruction. A group's potential eye-point becomes a false eye after a one-stone sacrifice — the surrounding stones end up self-ataring whenever they try to refill, so what looked like an eye no longer counts. - Setting up a snapback. Every snapback starts with a throw-in. More on this in a later section! - Liberty reduction in a capture race. Throwing a stone into the opponent's eye-space removes liberties from the inside, and the timing often decides which group dies first. - Starting a ko. Sacrificing one stone can convert a settled life-and-death position into a ko, where the defender now has to find ko threats to survive.

Example of a throw-in in a game

Where should black throw-in and what does it accomplish?

The throw-in is the smallest possible sacrifice — one stone — and one of the highest-leverage moves in the game. Learning to see the points where a throw-in works is one of the major steps from beginner to intermediate.