Larsen's Opening

Larsen's Opening begins with 1.b3: the pawn from b2 advances one square and clears b2 for the c1-bishop. Developing a bishop behind a pawn advanced one square is called a fianchetto. From b2, the bishop works along the long b2-e5-h8 diagonal and can pressure a Black pawn that occupies e5.

White does not immediately occupy d4 or e4, two central squares that White's pawns often contest from the start. In return, White keeps the freedom to advance the c-, d-, or e-pawn later and to develop the g1-knight to f3 according to Black's setup. The approach resembles the Réti: development and long-range pressure come first, with the central pawn arrangement decided later.

The b2-bishop pressures e5 without fixing White's center

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The bishop on b2 attacks e5 along the long diagonal and turns Black's central pawn into a target.

Long-range pressure preserves several structures

Black has occupied e5 and defended it with the knight, but White can still choose how to challenge the center.

1. The bishop on b2 attacks e5 along the long diagonal and turns Black's central pawn into a target.
2. The knight on c6 defends e5 while developing, so the bishop's pressure does not win the pawn by itself.
3. c4 contests d5 from the flank and can lead toward English Opening structures.
4. d4 chooses direct central occupation and adds another White attack on e5.
5. e3 and Nf3 form a development plan: they open the f1-bishop and add more pressure on e5 without deciding the c- or d-pawn yet.

The most useful comparison is with the Polish Opening. Both often place the bishop on b2, but 1.b3 moves the pawn only one square and keeps it relatively safe; 1.b4 gains more space but makes that pawn a more immediate target. It is also the queenside counterpart of the King's Fianchetto Opening, which begins with 1.g3.