The Triangle Defence is a name for the position than can arise after the following move orders:
- 1 Nf3 d5 2 d4 e6 3 c4 c6
- 1 Nf3 d5 2 d4 c6 3 c4 e6
- 1 Nf3 e6 2 c4 d5 3 d4 c6
Black can aim for independent variations, or he can look to transpose into either the Semi-Slav Defence or a form of the Stonewall Defence.
The most obvious reply for White is 4 Nc3, but then the point of Black’s move order can be seen. As well as 4 …Nf6, transposing into the Semi-Slav, Black can also opt for 4 …dxc4, the Abrahams (or Noteboom) Variation. Then the main line runs 5 a4 Bb4 6 e3 b5 7 Bd2 a5 8 axb5 Bxc3 9 Bxc3 cxb5 10 b3 Bb7 11 bxc4 b4 12 Bb2 Nf6, with an unclear position.
As White has trouble demonstrating an advantage in the above line, he has tried other approaches. The most flexible is 4 Qc2, advocated by both Khalifman in his “Kramnik” series, and Hilton and Ippolito in their first volume on Alex Wojtkiewicz’s repertoire. Alternatively, White can consider 4 e3, which is Avrukh’s choice, which doesn’t have to lead to the Meran Variation after 4 …Nf6, because White can hold back Nc3 and play instead one of 5 b3, 5 Bd3 and 5 Nbd2. However, it does allow Black to adopt a form of Stonewall with 4 …f5, when White cannot develop his bishop on f4, as he would like; instead 5 Bd3 is the way to go.