Triangulation

One of the ways of passing the move to the opponent. The classic example on the theme of triangulation is the following one (Fahrni — Alapin).

If it were Black to move in this position, Black would lose at once:

Boards can be stepped through with the mouse wheel, a swipe, or the arrow keys — not just the buttons below them. Interactive boards

12345678abcdefgh

1. 1.
3. 2.
4. 3.
5. 4.

The move is handed to Black as follows:

12345678abcdefgh

1. 1.
2. 2.
3. 3.
4. The goal is achieved. By walking the king around the triangle d5-d4-c4-d5, White has passed the move to Black