Pawn (chess)

The pawn (♙, ♟) is the most numerous piece in the game of chess and, in most circumstances, the weakest. It historically represents soldiers or infantry, or more particularly, armed peasants or pikemen. Each player begins a game with eight pawns, one on each square of the immediately in front of the other pieces. (The white pawns start on a2, b2, c2, d2, e2, f2, g2, h2; the black pawns start on a7, b7, c7, d7, e7, f7, g7, h7.)
Individual pawns are referred to by the on which they stand. For example, one speaks of "White's f-pawn" or "Black's b-pawn". Alternatively, they can be referred to by the piece which stood on that file at the beginning of the game, e.g. "White's king bishop's pawn" or "Black's queen knight's pawn". It is also common to refer to a ', meaning any pawn on the a- or h-files, a ' (on the b- or g-files), a ' (on the c- or f-files), a ' (on the d-file), a ' (on the e-file), and a ' (on the d- or e-files).
Placement and movement.
Unlike the other pieces, pawns cannot move backwards. Normally a pawn moves by advancing a single square, but the first time a pawn moves, it has the option of advancing two squares. Pawns may not use the initial two-square advance to jump over an occupied square, or to capture. Any piece immediately in front of a pawn, friend or foe, blocks its advance. In the second diagram, the pawn on c4 can move to c5; the pawn on e2 can move to either e3 or e4.
Capturing.
Unlike other pieces, the pawn does not capture in the same direction that it moves. A pawn captures diagonally forward one square to the left or right (see diagram).
Another unusual rule is the "en passant" capture. It can occur after a pawn advances two squares using its initial two-step move option, and the square passed over is attacked by an enemy pawn. The enemy pawn is entitled to capture the moved pawn "in passing" – as if it had advanced only one square. The capturing pawn moves to the square over which the moved pawn passed (see diagram), and the moved pawn is removed from the board. The option to capture the moved pawn "en passant" must be exercised on the move immediately following the double-step pawn advance, or it is lost for the remainder of the game. 
"En passant" was added in the 15th century to compensate for the then newly added two-square initial move rule (Hooper & Whyld 1992:124). Without "en passant", a pawn on its initial square could safely bypass a square controlled by an advanced enemy pawn. "En passant" is the only capture in chess in which the capturing piece does not replace the captured piece on the same square.
Promotion.
A pawn that advances all the way to the opposite side of the board (the opposing player's first rank) is "promoted" to another piece of that player's choice: a queen, rook, bishop, or knight of the same color. The pawn is immediately (before the opponent's next move) replaced by the new piece. Since it is uncommon for a piece other than a queen to be chosen, promotion is often called "queening". When some other piece is chosen it is known as "underpromotion". The piece most often selected for underpromotion is a knight, typically used to execute a checkmate or a fork to gain a significant net increase in material. Underpromotion is also used in situations where promoting to a queen would give immediate stalemate. The choice of promotion is not limited to pieces that have been captured; thus a player could in theory have as many as ten knights, ten bishops, ten rooks or nine queens on the board simultaneously. While this extreme would almost never occur in practice, in game 11 of their 1927 world championship match, José Raúl Capablanca and Alexander Alekhine each had two queens in play from move 65 through move 66. While some finer sets do include an extra queen of each color, most standard chess sets do not come with additional pieces, so the physical piece used to replace a promoted pawn on the board is usually one that was previously captured. In informal games, when the correct piece is not available, a second queen is often indicated by inverting a previously captured rook, or placing two pawns on the same square. In tournament games however this is not acceptable, and may result in the arbiter ruling that the upturned piece is, in fact, a rook.
Strategy.
The "pawn structure", the configuration of pawns on the chessboard, mostly determines the strategic flavor of a game. While other pieces can usually be moved to more favorable positions if they are temporarily badly placed, a poorly positioned pawn is limited in its movement and often cannot be so relocated.
Because pawns capture diagonally and can be blocked from moving straight forward, opposing pawns can become locked in diagonal of two or more pawns of each color, where each player controls squares of one color. In the diagram, Black and White have locked their d- and e-pawns.
Here, White has a long-term advantage. White will have an easier time than Black in finding good squares for their pieces, particularly with an eye to the . Black, in contrast, suffers from a on c8, which is prevented by the black pawns from finding a good square or helping out on the kingside. On the other hand, White's central pawns are somewhat and vulnerable to attack. Black can undermine the white pawn chain with an immediate ...c5 and perhaps a later ...f6.
Isolated pawn.
Pawns on adjacent files can support each other in attack and defense. A pawn which has no friendly pawns in adjacent files is an "isolated pawn". The square in front of an isolated pawn may become an enduring weakness. Any piece placed directly in front not only blocks the advance of that pawn, but cannot be driven away by other pawns.
In the diagram, Black has an isolated pawn on d5. If all the pieces except the kings and pawns were removed, the weakness of that pawn might prove fatal to Black in the endgame. In the middlegame, however, Black has slightly more freedom of movement than White, and may be able to trade off the isolated pawn before an endgame ensues.
Passed pawn.
A pawn which cannot be blocked or captured by enemy pawns in its advance to promotion is a "passed pawn". In the diagram, White has a "protected" passed pawn on c5 and Black has an "outside" passed pawn on h5. Because endgames are often won by the player who can promote a pawn first, having a passed pawn in an endgame can be decisive – especially a protected passed pawn (a passed pawn that is protected by a pawn). In this vein, a pawn "majority", a greater number of pawns belonging to one player on one side of the chessboard, is strategically important because it can often be converted into a passed pawn.
The diagrammed position might appear roughly equal, because each side has a king and three pawns, and the positions of the kings are about equal. In truth, White wins this endgame on the strength of the protected passed pawn, regardless which player moves first. The black king cannot be on both sides of the board at once – to defend the isolated h-pawn and to stop White's c-pawn from advancing to promotion. Thus White can capture the h-pawn and then win the game .
Doubled pawn.
After a capture with a pawn, a player may end up with two pawns on the same , called "doubled pawns". Doubled pawns are substantially weaker than pawns which are side by side, because they cannot defend each other, they usually cannot both be defended by adjacent pawns, and the front pawn blocks the advance of the back one. In the diagram, Black is playing at a strategic disadvantage due to the doubled c-pawns.
There are situations where doubled pawns confer some advantage, typically when the guarding of consecutive squares in a file by the pawns prevents an invasion by the opponent's pieces.
Pawns which are both doubled and isolated are typically a tangible weakness. A single piece or pawn in front of doubled isolated pawns blocks both of them, and cannot be easily dislodged. It is rare for a player to have three pawns in a file, i.e. "tripled" pawns.
Wrong rook pawn.
In chess endgames with a bishop, a may be the "wrong rook pawn", depending on the square-color of the bishop. This causes some positions to be draws that would otherwise be wins.
History.
The pawn has its origins in the oldest version of chess, chaturanga, and it is present in all other significant versions of the game as well. In chaturanga, this piece moved directly forward, capturing to the sides (one square diagonally forward to the left or right).
In medieval chess, an attempt was made to make the pieces more interesting, each file's pawn being given the name of a commoner's occupation. On the board, from left to right, those titles were:
The most famous example of this is found in the second book ever printed in the English language, "The Game and Playe of the Chesse". Purportedly, this book, printed by William Caxton, was viewed to be as much a political commentary on society as a chess book. 
The ability to move two spaces, and the related ability to capture "en passant", were introduced in 15th-century Europe (see "En passant" § Historical context). The rule for promotion has changed through history (see History of the promotion rule).
Etymology and word usage.
Although the name origin of most other chess pieces is obvious, the etymology of "pawn" is fairly obscure. It is derived from the Old French word "paon", which comes from the Medieval Latin term for "foot soldier" and is cognate with "peon". In most other languages, the word for pawn is similarly derived from "paon", its Latin ancestor or some other word for foot soldier. In some languages the pawn is named after a term for "peasant" or "farmer", reflecting how the lower orders were conscripted as footsoldiers in wartime: Hungarian "paraszt", Slovene "kmet", German "Bauer", Danish/Norwegian/Swedish "bonde", Latvian "bandinieks". In Irish, the term "fichillín", a diminutive of "ficheall" ("chess") is sometimes used, though the term "ceithearnach" ("foot soldier") is also used. In Thai the pawn is called เบี้ย ("bîia"), which signifies a cowrie shell or a coin of little value. In Turkish the pawn is called "piyon", borrowed from the French word in the 19th century.
"Pawn" is often taken to mean "one who is easily manipulated" or "one who is sacrificed for a larger purpose". Because the pawn is the weakest piece, it is often used metaphorically to indicate unimportance or outright disposability; for example, "She's only a pawn in their game."
Unicode.
Unicode defines two codepoints for a pawn:
♙ U+2659 White Chess Pawn (HTML &#9817;)
♟ U+265F Black Chess Pawn (HTML &#9823;)
References.
Bibliography