Irregular Chess Openings

An irregular chess opening is a traditional phrase for an unusual chess opening. Back in the early 19th century, anything except 1. e4 e5 or 1. d4 d5 was considered irregular. But as opening theory developed, openings that were formally "irregular" now have become standard. Unfortunately, because these openings are unpopular among chess players, few references actually cover then in detail. 

Usage of this term

This terms meaning is never precise and always varies between writers. 

One of the earliest references to "irregular openings" has been made by William Lewis is his 1832 work Second Series of Lessons on the Game of Chess. Lewis classified openings like this:   

• "King's Bishop Game" (1.e4 e5 2. Bc4)   
• "King's Knight Game" (1.e4 e5 2. Nf3)   
• "Queen's Bishop Pawn Game" (1. e4 e5 2. c3)
• "King's Gambit" (1. e4 e5 2. f4)
• "Queen's Gambit (1.d4 d5 2.c4)
• "Irregular Openings" (all other openings)

Carl Jaenisch, an early advocate of the French and Sicilian Defenses, rejected using the term "irregular". He said that openings should be classified as "correct", "incorrect", and "hazardous." Howard Staunton accepted Lewis's overall classification system. He wrote "Those methods of commencing the game, in which the first or second player moves other than (1.e4 e5 or 1.d4 d5) are usually designated "Irregular". Without assenting to the propriety of this distinction, I have thought it advisable, for the sake of perspicuity, to adopt a general and well known classification in preference to arranging these peculiar débuts under separate and less familiar heads." Under this heading, Staunton considers the following openings:

• French Defense
• Sicilian Defense
• Scandinavian Defense
• Owen's Defense
• Dutch Defense
• Benoni Defense
• Bird's Opening
• English Opening

Examples

The vast majority of high level chess games begin with 1. e4, 1. d4, 1. Nf3, or 1.c4. Also seen occasionally are 1. g3, 1.b3, and 1.f4. Anything other is considered an irregular chess opening and classified under the code A00 by the Encyclopedia of Chess Openings. Although they are classified under a single code, these openings are unrelated to each other. 

The openings classified under A00 are:

• 1.a3 Anderssen's Opening
• 1.a4 Ware Opening
• 1.b4 Polish Opening (a.k.a Sokolsky Opening)
• 1.c3 Saragossa Opening
• 1.d3 Mieses Opening
• 1.e3 Van't Kruijs Opening
• 1. f3 Barnes Opening
• 1. g3 Hungarian Opening
• 1. g4 Grob Opening
• 1.h3 Clemenz Opening
• 1. h4 Kadas Opening
• 1.Na3 Sodium Attack
• 1. Nc3 Van Geet Opening
• 1. Nh3 Amar Opening

Unusual Responses by Black

These are openings in which Black makes an unconventional response to 1. e4 and classified B00 (King's Pawn Game) Included in this code are:

• 1. e4 a6 St. George Defense
• 1. e4 b6 Owen's Defense
• 1. e4 f6 Branes Gambit

• 1. e4 Na6 Lemming Defense

• 1. e4 Nc6 Nimzowitsch Defense
• 1. e4 Nh6 Hippopotamus Defense
• 1. e4 a5 Ware Defense
• 1. e4 b5 Polish Gambit
• 1.e4 f5 Duras Gambit
• 1.e4 g5 Borg Defense
• 1.e4 h5 Goldsmith's Defense