Sokolsky Opening

The Sokolsky Opening, also known as the Orangutan and the  Polish Opening, is an uncommon chess opening that begins with the move:
 * 1. b4

According to various databases, out of the twenty possible first moves from White, the move 1.b4 ranks ninth in popularity. It is considered an irregular opening, so it is classified under the A00 code in the Encyclopaedia of Chess Openings.

Origins
One of the earliest opening plays of b4 was by Bernhard Fleissig playing against Carl Schlechter in 1893, although Fleissig was handily defeated in just 18 moves. Nikolai Bugaev defeated former world champion Wilhelm Steinitz with it in a simul exhibition game, and later published an analysis of the opening in 1903 in a Russian magazine article. Savielly Tartakower defeated Richard Réti using b4 in a match in 1919 when both were top-level players, and Reti himself defeated Abraham Speijer in Scheveningen 1923 using the opening.

The most famous use came in a game between Tartakower and Géza Maróczy at the New York 1924 chess tournament on March 21, 1924. The name "The Orangutan" originates from that game: the players visited the Bronx Zoo the previous day, where Tartakower consulted an orangutan named Susan. She somehow indicated, Tartakower insisted, that he should open with b4. Also, Tartakower was impressed with the climbing skills of the orangutan, and thought that the "climb" of the b-pawn was similar. In that particular game, Tartakower came out of the opening with a decent position, but the game was ultimately drawn.

The opening received sporadic play in the decades that followed. Tartakower had more success in 1926 when he used it against Edgard Colle for a victory. One of the most notable proponents was the Soviet player Alexei Pavlovich Sokolsky (1908–1969), who often used it in high-level play. Sokolsky wrote a monograph on the opening in 1963, Debyut 1 b2–b4, which would lead to the opening being called the "Sokolsky Opening". Sokolsky's work defended the viability of the opening even at the highest levels of professional play.

The final term, and the one used in contemporary books and chess websites such as Chess.com and Lichess, is the Polish Opening. This is by analogy to the Polish Defense (1. d4 b5), where Black's Queen's Knight pawn is advanced two spaces.

Notable later usage
In general, the opening is not popular at the top level. Alexander Alekhine, who played in the same 1924 New York tournament as Tartakower and the Orangutan game, wrote that the problem is that it reveals White's intentions before White knows what Black's intentions are. That said, it still sees sporadic use among top level grandmasters. Boris Spassky used it against Vasily Smyslov in a 1960 match, albeit having to settle for a draw. In May 2021, world champion Magnus Carlsen essayed the opening against GMs Hikaru Nakamura and Wesley So in the online FTX Crypto Cup rapid tournament.

Details
The opening is largely based upon tactics on the or the f6- and g7-squares. Black can respond in a variety of ways: For example, a common response is for Black to make a claim on the, which White's first move ignores, with 1...e5 (it is normal for White to ignore the attack on the b-pawn and play 2.Bb2, where 2...d6, 2...f6, and 2...Bxb4 are all playable), 1...d5 (possibly followed by 2.Bb2 Qd6, attacking b4 and supporting ...e7–e5), or 1...f5. Less ambitious moves like 1...Nf6, 1...c6 (called the Outflank Variation, preparing ...Qb6 or ...a5), and 1...e6 are also reasonable. Rarer attempts have been made with 1...a5 or 1...c5. Black's reply 1...e6 is usually followed by ...d5, ...Nf6 and an eventual ...c5. After 1...a5 White will most likely play 2.b5 and take advantage of Black's queenside weakness. Black's 1...c5 is much sharper and more aggressive and is normally used to avoid theory. After the capture Black will generally place pressure on the c5-square and will develop an attack against White's weak queenside structure at the cost of an inferior central position.

Named variations

 * 1…b5 (Symmetrical Variation)
 * 2.a4 (Queen's Knight's Gambit)
 * 1...c5 (Birmingham Gambit)
 * 1...c6 (Outflank Variation)
 * 1...c6 2.Bb2 a5 3.b5 cxb5 4.e4 (Schuhler Gambit)
 * 1...d5 2.Bb2 c6 3.a4 (Myers Variation)
 * 1...d5 2.Bb2 Qd6 3.a3 e5 4.Nf3 e4 5.Nd4 Nf6 6.c4! dxc4 7.e3 Be7 8.Bxc4 O-O 9.Nc3 (German Defense)
 * 1...e5 2.a3 (Bugayev Attack)
 * 1...e5 2.Bb2 c5 (Wolferts Gambit)
 * 1...e5 2.Bb2 f6 3.e4 Bxb4 (Tartakower Gambit)
 * 1...e5 2.Bb2 f6 3.e4 Bxb4 4.Bc4 Nc6 5.f4 Qe7 6.f5 g6 (Brinckmann Variation)
 * 1...Na6 (Bucker Defense Kingsley Variation)
 * 1...Nc6 (Grigorian Variation)
 * 1...Nf6 2.Bb2 g6 3.g4 (Polish Spike)
 * 1...Nh6 (Karniewski Variation)