King's Indian Attack
The fastest way to fianchetto the king's bishop and castle is the King's Indian Attack (KIA), the reverse of the King's Indian Defense. White just plays Nf3, g3, Bg2, and 0-0, before seeing how to proceed.
The KIA also refers to a plethora of systems for White involving pawns on d3, g3, and e4; knights on d2 and f3; a kingside fianchetto and kingside castling. This KIA setup can be used after 1.e4 against the Sicilian Defense, French Defense, Caro-Kann Defense, and many other popular openings for Black. White often plays for a kingside attack with Black trying to win on the queenside.
Starting Position
The King's Indian Attack, when referring to a specific opening, generally starts with either 1.Nf3 d5 2.g3 or 1.Nf3 Nf6 2.g3.
A kingside fianchetto with Nf3 is an idea in several other openings as well, most notably the French Defense variation 1.e4 e6 2.d3, but also in the Sicilian, Caro-Kann, and others.
Pros
- Flexible
- May lead to a kingside attack
- Not very theoretical
Cons
- Allows Black a strong center
- Gives Black many different options
- Does not put immediate pressure on Black
Variations
There are many variations of the KIA, but the main question regardless is Black's decision with the c-pawn: Play ...c6 to blunt the fianchettoed bishop's diagonal, or play ...c5 to gain extra queenside space? This choice also determines where Black's b8-knight will go: behind the c-pawn on c6 or to d7.
Oftentimes Black will play not only ...c5 but ...b5 and ...a5 and try to win on the queenside before White can breakt hrough on the kingside, as in the following possible move order.
Some specific early variations are below.
Yugoslav Attack (2...Nf6)
Whichever order Black plays the first two moves ...Nf6 and ...d5, it's the Yugoslav Variation. It's the most common way to meet Nf3 and g3 from White, both developing and beginning to claim the central space that White has foregone.

Keres Variation (2...Bg4)
The Keres Variation, named for GM Paul Keres, is mainly a move order subtlety where Black develops the c8-bishop as quickly as possible, to be followed up with ...Nd7 and ...c6.

Sicilian Variation (2...c5)
Black can also immediately announce the intention to claim as much space as possible with ...c5 on move two. It essentially creates a reverse King's Indian Defense and play often continues in that vein with something like 3.Bg2 Nc6 4.O-O e5 or 4...Nf6.

History
Like several hypermodern openings, the King's Indian Attack was first known to be played by Bonnerjee Mohishunder in his games with John Cochrane in Calcutta (Kolkata), India in the 1850s, but did not become more widely popular until the 1920s.
The heyday of the KIA was the 1960s when GMs Pal Benko and Bobby Fischer won regularly with it, as IM Jeremy Silman discusses here. Although now less popular at the GM level, it can be used when someone desperately needs a win as White, and remains a good option for more casual players.
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The Polish Opening, also known as the Sokolsky or the Orangutan, is the opening 1.b4 by White. Although only the ninth-most popular opening move, it's a respectable option with some devoted followers. Instead of playing in the center, White fights for an advantage on the queenside.
Starting Position
The Polish is very distinctive and once 1.b4 is played, a game is in the Polish Opening with little chance at transposing into something else.
Pros
- Gains queenside space
- Can catch Black off guard
- Prepares to fianchetto the dark-squared bishop
Cons
- Doesn't control the center
- b-pawn can become a target
- Prepared opponents can cause White difficulties
Variations
Black has several viable options against the Polish. Here are the most popular.

1...e5
Black's most common response is 1...e5, immediately attacking the b-pawn. Often a trade follows with 2.Bb2 Bxb4 3.Bxe5. Although this trade's a central Black pawn for a wing White pawn, Black scores very well. Black does less well defending the e-pawn with either 2...d6 or 2...f6 but both are playable.

Schiffler-Sokolsky
Black's next two most popular moves are 1...d5 and 1...Nf6 and they often transpose into the same line, the Schiffler-Sokolsky. Black has more central space while White gains further queenside space by pushing the b-pawn again. The most common move order is given below.
1...c6
The idea behind this move, the Outflank Variation, is to attack the b-pawn with 2...Qb6.
History
The two players most associated with 1.b4 are Polish GM Savielly Tartakower (1887-1956) and Soviet IM Alexey Sokolsky (1908-1969), hence the common names for the opening: the Polish (more common in the West) and the Sokolsky (more so in Russian sources). The third name, the Orangutan, is also thanks to Tartakower. During the 1924 New York tournament he visited the Bronx Zoo and something inspired him to play the move and name it for that primate.
It was an obscure 19th-century British player, however, who first played 1.b4: Arthur Skipworth in 1868, a game Skipworth won. Maybe we don't call it the Skipworth Opening because that makes it sound like it's worth skipping.
Although rare, the Polish Opening isn't bad and it can lead to unique positions that are interesting to play.