Difficulty: Intermediate   Keywords: Tactics

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

123 principle

Don't play B1, W2, B3: just play B3.

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 B1/W2 exchange was something of a loss, then you should also consider that a player with better foresight would have tried to skip over it.


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

Hane-descend is poor  

Here, after black+circle is answered by white+circle, it is usually wrong to continue with B1. That allows W2 forcing Black to defend.

Just playing B1 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.

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. B1 will often be correct, rather than Black's atari play at either of a or b.

For more examples, see

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 B1/W2 and then playing tenuki as Black with B3 may be bad, if W4 can make playing B1 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 B1 and W2 isn't typically kikashi - effective forcing play - because White a is now better than it was before B1 was played.

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

One-Two-Three last edited by on March 11, 2014 - 14:22
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