We have already got acquainted with the main difference between renju – fouls, and we can now ask ourselves: besides the fact that the second player (white) has no fouls, can he somehow use the restrictions of his opponent? Consider this position:

pressure

We see that Black has two pairs, and there is also a move that can make two triples out of them at once, i.e. foul point (marked with an X). At the same time, White has only one pair, can he somehow qualitatively use Black’s limitations for himself? It turns out they can. The move to X forms a triple, which Black will simply close on one of the sides (for example, by moving to A). It is not difficult to make sure that after winning back the three of a kind, White will not have any more resources (the pair will become a three of a kind), and the foul point will disappear. But why would White himself go to this point? Remembering that Black cannot legally move to X, White surrounds it, trying to force Black to do so. How? Building threats, of course. As a variant of the encirclement of point X, a move to A is suitable.

foul catching

With move 1, White creates a threat – a breaking three, to which Black must react, but due to a foul, it cannot be closed to the center. After closing, White is again in no hurry to move to X, remembering that according to the rules it is forbidden for Black to go there, White once again surrounds this point, but this time leaving Black no choice. If Black moves to X, they will lose because they build a foul 3 * 3, but if Black does not do this, then White will build a five on the next move by going to X. Thus, it turns out that White can win in renju even without the help of forks, using only the restrictions of his opponent, – “catch a foul”, i.e. force the opponent to make an illegal move. But it is not always easy and often a foul on the board still needs to be built. Consider another position:

construction

Obviously, there is no foul point on the board at the moment, but White can try to create one: there is only one black stone in C before the foul point at X, and White can get it. Black will respond to three A and B, but to four Y black will have to go to C, having built a foul for himself, after which White catches a foul (by going D or E). White can also catch another 3×3 foul at Y.

foul1

White does not always need a lot of resources or space to build and catch a foul, as, for example, in this position:

prefol

The position looks in Black’s favor, Black has two pairs and a very dangerous cluster of stones on the right, while White has only one pair. However, this is enough for them to win:

foul2

With each move, White creates new resources and at the same time does something useful: with two moves he builds a foul, and with the third he catches it.

The conclusion that suggests itself is that White needs much less resources and space to win than Black. This is the whole essence of renju – Black pays for the initial initiative not so much by a number of restrictions for himself, but by simplifying the task of his opponent at the end of the game, in case White fights back, of course.

We have considered cases where White can profitably use Black’s restrictions. In the next part, we will talk about the third difference between renju and tic-tac-toe – opening regulations.

In this thread, you learned:
What is foul pressure
How White Can Win Without Forks