Larsen's Opening (also called the Nimzo–Larsen Attack or Queen's Fianchetto Opening) is a chess opening starting with the move: 1. b3 It is named after the Danish grandmaster Bent Larsen. Larsen was inspired by the example of the great Latvian-Danish player and theoretician Aron Nimzowitsch (1886–1935), who often played 1.Nf3 followed by 2.b3, which is sometimes called the Nimzowitsch–Larsen Attack. It is classified under the A01 code in the Encyclopaedia of Chess Openings. The flank opening move 1.b3 prepares to fianchetto the where it will help control the central squares in hypermodern fashion and put useful pressure on Black's . The b2-bishop is often a source of recurring irritation for Black, who should not treat it lightly. Although Larsen was initially very successful with this opening, it suffered a setback in the 1970 USSR vs. Rest of the World match in Belgrade, where Larsen played it against reigning world champion Boris Spassky and lost in 17 moves. Larsen was also decisively defeated when playing it against Rosendo Balinas, Jr. at Manila in 1975. Notably, this opening received interest from Bobby Fischer the same year, who employed 1.b3 on at least five occasions, winning all five, including games with GM Miroslav Filip, GM Henrique Mecking (Palma de Mallorca 1970 Interzonal), GM Vladimir Tukmakov (Buenos Aires 1970), and GM Ulf Andersson (Siegen 1970). Today, Larsen's Opening is occasionally used at the GM-level, with top grandmasters Hikaru Nakamura, Richárd Rapport, and Baadur Jobava employing it successfully. Popularity The move 1.b3 is less popular than 1.g3 (Benko's Opening), which prepares a quick castling. According to ChessBase, 1.b3 ranks sixth in popularity out of the possible 20 first moves while the fifth-ranking 1.g3 is about three times as popular. Larsen frequently used unconventional openings of this sort. He believed it to be an advantage in that Black, usually unfamiliar with such openings, is forced to rely on his own abilities instead of relying on memorised, well-analysed moves of more common White openings. Main lines Black has several options to meet 1.b3. The most common are: 1...e5, the Modern Variation, is the most common response, making a grab for the centre and limiting the scope of the white bishop. Play typically continues 2.Bb2 Nc6. Then the Main line is 3.e3 d5 4.Bb5 Bd6 5.c4. After 2.Bb2 Nc6, 3.f4 is the Paschmann Gambit. After 2.Bb2, 2...f5 3.e4 is called the Ringelbach Gambit. 1...d5, the Classical Variation, is