"Don't surround territory with thickness."

Intro

• Territory (not necessarily thick)

• Influence (not necessarily thick)

• Thickness

Among the many Go proverbs, this one is perhaps one of the most effective ones. If we look at attack, sabaki, and shinogi, it happens to be that learning how to attack is a prerequisite to learning how to fight back or live. Only when you know how to attack well can you defend against it.

This may prompt us to play simple fighting games with openings like sanrensei, but when we build outside thickness, how do we use it well? Consider this metaphor.

In this business of Go, we must use our assets (thickness in this case) to generate profit. So given this factory, how do we make a profit of maybe ten, fifteen, or twenty points?

Now, we might compare two options:

1 Get whatever points you can next to the wall (sell the factory)

or,

2 Use the thickness to surround a weak group and use the outcome to make points (make products)

But of course, we want to use the thickness to surround a weak group and use the outcome to make points. Factories aren't meant to generate profit by selling the land, the building, or the machines. It's not that we can't sell the factory, but this conversion isn't the intended purpose of a factory. If we use the factory as intended, we can generate more profit than if we sell it. Let's take a look at what I mean.

Example:

Black to Play

Take a look at the above game state. If you look at the top right quadrant, we see a massive thickness for black. And on the right side, near the center, white has a weak group. Now let's think about how we can use this thickness to generate an attack!

There are many options here, but here is one move that has many good attacking follow-ups.

One follow-up that the move aims at is this: to threaten the four white stones on the bottom with a surround.

So a natural response by white would be to defend by preventing black from playing the above continuation.

Black then continues by capping the weak group in the center. You could say that the cap is the epitome of an attacking move. Let's see how this unfolds.

White attaches to the capping stone and tries to settle his group, but black is fine just pushing white towards his thickness. It's suspicious whether white is alive here, but black isn't aiming to profit from the attack by killing this group.

What black is actually aiming for with this attack is to create territory. Now that black has used his thickness to attack (cap and surround), he has generated a secondary thickness facing the left side of the board. Black takes up position on the left side with two approach moves and the star point on the side.

Use thickness to surround a weak group and use the outcome(secondary influence) to make points(via territory-moyo)

But what's the difference between the first thickness and this second thickness? Why do we try to make this second thickness territory? Doesn't it go against everything I just explained? Well, let me introduce you to the distinction between a moyo and a ji-moyo.

Simply put, there is thickness and then there is thickness that is likely to become a lot of territory.

Let's go back to black's first move and play to surround territory with the thickness instead of attacking and see how this looks. Black plays this knight's move to make territory with the wall.

White responds and black responds, staying consistent with his plan to make any territory that he can with the wall.

White then roughly connects up and we can see, that black has gained a little bit of territory, minus what white got, adding up to very little profit in total. Because white is perfectly fine with this result, black has not created a lead yet. But given the fact that white had a weak group near black's army, there must have been a way to drive the weak group into our line of soldiers to really put the pressure on white's overall position.

Let's compare this result with the variation where black attacks instead. Black plays from the far side of the wall and routes the enemy toward the main army, and in exchange for giving up the potential to make territory in that area where white is cornered, black has generated a new wall which can be used to create a territory-moyo.

Notice the contrast between white's poor position and black's expansive position. When you can use your thickness to attack a weak group to create a second wall to build a ji-moyo with, we are using the factory as intended to generate the most profit, and this is the essence of how to think about thickness.

Finally, let's look at the two results side by side and really take in the difference.

The difference is astonishing, isn't it? On the left, black successfully used his power to break up white's position in a way that supports his expansion. Black is up by 9.5 points with a 96.7% chance to win this game, according to Katago.

On the right, black wielded power timidly and as a result, all of black's stones are overconcentrated on just the right side of the board while white has claimed everything else. White is up by 8.3 points with a 96.4% chance to win.

Conclusion

By focusing on just defending your points when you have power, you are missing out on an opportunity to accomplish multiple things at once. By using your influence (thick wall with no defects) to attack, you can force your opponent to play defensive moves that make very little points. And you deny the interesting direction of play. On top of this, you get to play the expansive moves that potentially both players were looking at for future development.

So when you have thickness, "Don't surround territory with thickness", instead, "surround a weak group with it", and you will be able to generate the positive exchange that power and flexibility can often afford.

And as you gain experience and refine your intuition, perhaps you too will feel the stones humming with a latent power...

-Hiro Nakae