Jetan, also known as Martian Chess, is a chess-based strategy game with unclear rules. It was created by Edgar Rice Burroughs as a game played on Barsoom, his fictional version of Mars. The game was introduced in The Chessmen of Mars, the fifth book in the Barsoom series. Its rules are described in chapter 2 and in an appendix of the book.
Board and pieces
Jetan is played on a black and orange checkerboard of 10 rows by 10 columns, with orange pieces on the "north" side and black pieces on the "south".
Each player has the following playing pieces: one Chief, one Princess, two Fliers; two Dwars (Captains); two Padwars (Lieutenants); two Warriors; two Thoats (Mounted Warriors); and eight Panthans (Mercenaries). The Chief, Princess, Fliers, Dwars, Padwars and Warriors are positioned along the row closest to the player, with the Chief at left center, the Princess at right center, and the Fliers, Dwars, Padwars and Warriors arranged to flank each, with the Fliers innermost and the Warriors outermost. The Thoats and Panthans are positioned along the next row out from the player, with the Thoats flanking the Panthans. The complete arrangement of each side follows:
T p p p p p p p p T W P D F C P F D P W
Panthans are limited to one step per move. Other pieces take two or three. They may change their direction of movement at each step in the course of a move, so long as this is in a direction permitted for that piece. Each must take the full number of steps specified for it. No piece can cross the same square of the board twice during the course of a move. The Princess, Fliers, and Thoats may jump over a piece that is in their path.
A capture is made when a piece lands on a square occupied by an opposing piece with its final step or jump; the Princess may not make such a move.
The pieces move as follows:
- The Chief takes three steps in any direction.
- This is equivalent to three moves of a chess king, except that it cannot double back and may only capture at the third step.
- The Princess takes three steps in any direction; it may jump over other pieces but cannot capture.
- It may make one "escape" per game, jumping to any unoccupied space on the board.
- The Flier takes three steps diagonally; it may jump over other pieces.
- Per Burroughs, in an older version of Jetan these pieces were called Odwars.
- The Dwar takes three steps orthogonally.
- The Padwar takes two steps diagonally in any direction, or combination.
- The Warrior takes two steps in any direction or diagonally.
- The Thoat take two steps, of which one is orthogonal and the other diagonal; it may jump over intervening pieces.
- The Panthan takes one step in any direction but backwards.
In Burroughs' description, Jetan is won when either a Chief captures the opposing Chief, or when any piece captures the opposing Princess. The game is drawn if each player is reduced to three or fewer pieces of equal value and it is not won within the next ten moves, or if a Chief is taken by any piece other than a Chief.
These rules result in too many draws for the tastes of most players, so a number of variants have been proposed to address this issue, the simplest being that the capture of a Chief by a piece other than a Chief merely retires the Chief, without drawing or ending the game.
Jetan in Burroughs' novels
According to The Chessmen of Mars, Jetan was said to represent an ancient war between the Yellow and Black races of Barsoom. This explains why the orange pieces begin on the "north" side and black pieces on the "south", because Barsoom's Yellow and Black races inhabit its north and south polar regions, respectively.
The second half of The Chessmen of Mars takes place in the city of Manator, where the most popular civil event involves human beings fighting to the death in a life-sized Jetan game viewed by hundreds of spectators. The "board" is large enough that some of the pieces are mounted on thoats and yet still fit in a single "square". However, this life-and-death version departs from the rules of Jetan in one very significant way: When one piece lands on a square occupied by another, the first does not automatically replace the second. Rather, the two pieces fight to the death, and the winner of the swordfight wins the square. The lone exception involves the Princess: if one side's piece lands on a square occupied by the other side's Princess, no battle occurs, and the first side wins the game.
Similar games in other fiction
Burroughs' Jetan may have inspired authors of later planetary romances to invent similar extraterrestrial versions of chess fought with human beings. Instances of such homage include:
- Lin Carter's Darza, from Renegade of Callisto, eighth volume in his Callisto series
- Kenneth Bulmer's Jikaida, from A Life for Kregen, 19th volume in his Dray Prescot series
- John Norman's Kaissa, mentioned many times in his Gor series, although never fully described
- S. M. Stirling's Atanj, from In the Courts of the Crimson Kings, his own Burroughs-influenced novel of an alternate Mars, also not fully described
- To complete.
- Padwar: It is unclear whether this means the piece may take two steps, or must take two steps.
X X X . . X O X . . X X X
If it must, then an opposing piece in a [.] square would block the padwar (at [O], which could not move to an [X] square in that direction. If not, then the padwar could capture a piece at [.]. Presumably it may only capture once per turn.
- Warrior: The meaning of this move is opaque. The text says "straight in any direction, or diagonally, two spaces", whereas the appendix says "2 spaces straight in any direction or combination". It is unclear whether this means that the piece may move two squares or must move two squares. From the text, this might mean moving like a chess king, but with twice the range; the text does not say whether the two steps must be in the same direction. From the appendix, the result would be a pattern like this if two steps are required:
X X . X X . O . X X . X X
The piece (at [O]) may only move to a square [X] if the space at [.] is not occupied. If the warrior may take up to two steps, then it may also move to the [.] squares. Presumably it may only capture once per turn.
- Because of the wording describing the change in direction ("one straight and one diagonal, and may jump intervening pieces"; "2 spaces, one straight and one diagonal in any direction"), it is clear that both steps are required. This suggests that both steps are required for the Padwar and Warrior.
- Panthan: The text says "one space in any direction except backward", and the appendix "1 space, forward, side, or diagonal, but not backward". A literal reading of the text would imply that backwards diagonal steps are not allowed, but the appendix suggests they are. Not allowing such moves (a "chained panthan") means that the panthans become stranded upon reaching the final rank, as they cannot retreat, whereas allowing such moves (a "free panthan") opens that file for the opponent, which creates more strategic interest.