One-Two-Three

Table of contents 123 principle Example Example 2 A more elaborate treatment Don't play out miai Forced answer advice James Kerwin on urgent plays: Bad tenuki Theory of reversible plays

Table of diagrams [Hane-descend] is poor [Hane-connect] Staircase - just connect Staircase - just connect Staircase - just connect Black hasn't gained

123 principle

Don't play , , : just play .

For example, in atari-connect combinations, the atari should often be omitted and only the move that would connect should be played.

A more verbose version of the principle reads

If, given the benefit of hindsight, you as Black can see that the / exchange was something of a loss, then you should also consider that a player with better foresight would have tried to skip over it.

Example

An example that comes up early in everyone's go career:

Hane-descend is poor  

Here, after is answered by , it is usually wrong to continue with . That allows forcing Black to defend.

Hane-connect  

Just playing is correct (in almost all cases). Now Black has the good follow-up endgame play at the circled point. And there remains some aji of the clamp at the square-marked point, too.

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Example 2

Staircase - just connect  

Should Black play atari here?

Staircase - just connect  

Or here?

Staircase - just connect  

This staircase shape is a reasonable example of the 123-principle. will often be correct, rather than Black's atari play at either of a or b.

For more examples, see

• One-Two-Three example 1
• One-Two-Three example 2
• One-Two-Three example 3
• One-Two-Three example 4
• One-Two-Three example 5
• One-Two-Three example 6

A more elaborate treatment

This principle is an aspect of:

Don't play out miai

In the absence of a good reason, true miai points should probably not be played out, as an unmotivated exchange a-b.

Forced answer advice

If you play a which you expect the opponent to answer at b, treating a as a forcing move, you should already know your follow-up play c. (From Tokimoto Hajime 8 dan.)

James Kerwin on urgent plays:

Treat a play at c as urgent if the opponent's play at b otherwise puts your earlier play at a at risk of being made meaningless. (Noted on play urgent moves before big moves.)

Bad tenuki

Playing / and then playing tenuki as Black with may be bad, if can make playing meaningless (see previous comment), or worse.

This might lead one to the

Theory of reversible plays

From CGT there is the quite profound idea of a reversible play. It again relates to thinking about a three-move 'block': Black a gives White an answer b which (probably) gives a position at least as good as the initial one, so Black ought to have the next play c lined up.

Black hasn't gained  

In this example the point is that Black has gained nothing yet, if we're just talking endgame. Simply playing and isn't typically kikashi - effective forcing play - because White a is now better than it was before was played.

See detailed discussion now at reversible play - loss and gain.