One-Two-Three

  Difficulty: Beginner   Keywords: Tactics

There are a few ideas about three-move sequences that come up quite frequently.

Discussion here moved to /Discussion.


123 principle (concise)

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.

123 principle (verbose)

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:

[Diagram]

Hane-descend is poor

Here, after BC is answered by WC, 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.


For more examples, see


A more involved case of the same idea is:

ABC principle

If Black has the choice of Black a, White b, Black c or Black b, White a, Black c, perhaps Black should simply play c.


[Diagram]

Staircase - just connect

This staircase shape is a reasonable example of the ABC principle. B1 will often be correct, rather than Black's atari play at either of a or b.


This is one 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.

Some more related ideas:

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.


[Diagram]

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.


This is a copy of the living page "One-Two-Three" at Sensei's Library.
(OC) 2005 the Authors, published under the OpenContent License V1.0.
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