Martian games
Edgar Rice Burroughs’ Jetan rules are, in some respects, vague and ambiguous. That has been known for a long time, and remains one of the reasons why the game has never gained wider recognition. The reasoning in this article is equally valid for Jetan and Thuria Jetan.
One Jetan ambiguity that has received very little attention regards threats to the Princess. The original rules simply state: “The Princess may not move onto a threatened square.” The reason why this is ambiguous is best understood when compared with Chess. Consider the corresponding FIDE law: “Leaving one’s own king under attack, [or] exposing one’s own king to attack ... is not allowed.”
In reality, there are three different situations that need to be covered by this kind of rule:
Only the last of these situations is covered by the Jetan rule, whereas the corresponding Chess law covers all three (the second phrase covers both situations 2 and 3).
George Fergus, who wrote a proposal for Jetan standard rules around 1965, was probably the first to address this problem. Fergus notes exactly the same division that we find in the Chess laws: “It is my feeling that consistent board games should have both of these rules rather than one or the other of them alone, since they are essentially two aspects of the same idea—that a player may make no move which would expose his Princess to attack.” Fergus comes to a pretty radical conclusion, noting that “neither of these two rules is necessary to the game, since anyone who is foolish enough to expose his Princess to attack ought to lose the game” (original underlining). He therefore suggests that the rule should be omitted, rather than amended or revised.
There is one aspect, however, that Fergus failed to consider, an aspect that topples his tower of arguments: Jetan has two royal pieces.
In a 1999 article, Taylor Kingston approaches the same problem from a different angle. How, he wonders, can you force the capture of Chief by Chief? One possibility that he comes up with is a situation such as described in the following diagram:
One Jetan ambiguity that has received very little attention regards threats to the Princess. The original rules simply state: “The Princess may not move onto a threatened square.” The reason why this is ambiguous is best understood when compared with Chess. Consider the corresponding FIDE law: “Leaving one’s own king under attack, [or] exposing one’s own king to attack ... is not allowed.”
In reality, there are three different situations that need to be covered by this kind of rule:
- An opponent's piece moves to attack the Princess/King.
- The moving of another friendly piece would put the Princess/King under threat (called a “pin” in traditional Chess tactics).
- The Princess/King is actively moved onto a threatened square.
Only the last of these situations is covered by the Jetan rule, whereas the corresponding Chess law covers all three (the second phrase covers both situations 2 and 3).
George Fergus, who wrote a proposal for Jetan standard rules around 1965, was probably the first to address this problem. Fergus notes exactly the same division that we find in the Chess laws: “It is my feeling that consistent board games should have both of these rules rather than one or the other of them alone, since they are essentially two aspects of the same idea—that a player may make no move which would expose his Princess to attack.” Fergus comes to a pretty radical conclusion, noting that “neither of these two rules is necessary to the game, since anyone who is foolish enough to expose his Princess to attack ought to lose the game” (original underlining). He therefore suggests that the rule should be omitted, rather than amended or revised.
There is one aspect, however, that Fergus failed to consider, an aspect that topples his tower of arguments: Jetan has two royal pieces.
In a 1999 article, Taylor Kingston approaches the same problem from a different angle. How, he wonders, can you force the capture of Chief by Chief? One possibility that he comes up with is a situation such as described in the following diagram:
Kingston writes: “In this position Black’s Dwar on C5 is pinning the orange Chief, as he cannot move off the C-file without exposing the Princess to check. Now by moving his Chief to B4, B5, C4, D4, E4, or E5, Black would be in position next move to capture his paralyzed counterpart and win.” Some of Kingston’s square references are wrong, and have been corrected. (It should be noted that Kingston missed one step in his analysis, so that if black were to move to E5, for example, orange Princess would be threatened by black Chief, after which moral constraints no longer stop orange Chief from moving out of his pin to attack black Chief. This kind of situation is covered in no version of the rules, neither Burroughs' nor Fergus' nor mine. I will not further discuss this situation here, since it is beside the point I want to make.)
A situation such as described by Kingston requires clear rules for how to handle the Princess under threat. In Fergus’ interpretation, orange Chief can capture black Chief, because there is no rule against passively or actively exposing your Princess to threat. In fact, Kingston comes to the same conclusion, but through different reasoning: “My view is that the Chief capture, by occurring first, would take precedence, and thus Orange could capture and win.”
Even so, Kingston’s analysis shows exactly why Fergus’ conclusion, that these rules are unnecessary, is wrong—because it is not only about the Princess. The Chief is there, also, and whenever the Chief is nearby, the dynamics involved when threatening the Princess change dramatically, as seen in Kingston’s example. The main reason for this is that the Chief and Princess are not equal: The Princess constantly needs to be protected from the other player, whereas a Chief by Chief capture is very difficult. This inequality, built into the rules, must be the reason why Burroughs added his incomplete rule about the Princess under threat, and it is also the reason why the rule should be amended, rather than deleted.
Another aspect is Jetan’s infamous tendency to draw often. The problem with the many draws depends to a large extent on the playing styles of the players, and there are too few recorded games to say anything certain about how widespread the “draw issue” really is. Yet, it is generally perceived as a problem, and therefore needs to be addressed. Amending the rule here discussed would potentially allow for more “Chief captures Chief” victories, thereby possibly decreasing the number of draws. Even though it would perhaps be a very marginal difference in practice, I feel that every rule or interpretation that helps to reduce the number of draws is a good thing.
Now I am going to be honest: In my own games of Jetan, or in any other people’s games that I saw recorded, I only experienced a single occasion where such a rule would make a difference to the outcome. That was in the Thuria Jetan game recorded and annotated below. After move 39, Black has the option to move his Flier to B7 to threaten Orange Chief, but if he were to do that, Orange could have moved 40....Pt E3–E2 (+), thereby winning material (the Panthan avoids capture), gaining a tempo and forcing the Princess to retreat, because Black must move out of the threat to the Princess before he can address his attack on the Orange Chief. Thus, Black had to consider other options and decided to capture Panthan with Warrior, forcing his Warrior into an exposed position, which eventually decided the game in the Orange player’s favour.
A situation such as described by Kingston requires clear rules for how to handle the Princess under threat. In Fergus’ interpretation, orange Chief can capture black Chief, because there is no rule against passively or actively exposing your Princess to threat. In fact, Kingston comes to the same conclusion, but through different reasoning: “My view is that the Chief capture, by occurring first, would take precedence, and thus Orange could capture and win.”
Even so, Kingston’s analysis shows exactly why Fergus’ conclusion, that these rules are unnecessary, is wrong—because it is not only about the Princess. The Chief is there, also, and whenever the Chief is nearby, the dynamics involved when threatening the Princess change dramatically, as seen in Kingston’s example. The main reason for this is that the Chief and Princess are not equal: The Princess constantly needs to be protected from the other player, whereas a Chief by Chief capture is very difficult. This inequality, built into the rules, must be the reason why Burroughs added his incomplete rule about the Princess under threat, and it is also the reason why the rule should be amended, rather than deleted.
Another aspect is Jetan’s infamous tendency to draw often. The problem with the many draws depends to a large extent on the playing styles of the players, and there are too few recorded games to say anything certain about how widespread the “draw issue” really is. Yet, it is generally perceived as a problem, and therefore needs to be addressed. Amending the rule here discussed would potentially allow for more “Chief captures Chief” victories, thereby possibly decreasing the number of draws. Even though it would perhaps be a very marginal difference in practice, I feel that every rule or interpretation that helps to reduce the number of draws is a good thing.
Now I am going to be honest: In my own games of Jetan, or in any other people’s games that I saw recorded, I only experienced a single occasion where such a rule would make a difference to the outcome. That was in the Thuria Jetan game recorded and annotated below. After move 39, Black has the option to move his Flier to B7 to threaten Orange Chief, but if he were to do that, Orange could have moved 40....Pt E3–E2 (+), thereby winning material (the Panthan avoids capture), gaining a tempo and forcing the Princess to retreat, because Black must move out of the threat to the Princess before he can address his attack on the Orange Chief. Thus, Black had to consider other options and decided to capture Panthan with Warrior, forcing his Warrior into an exposed position, which eventually decided the game in the Orange player’s favour.
But if this rule only comes in play that rarely, then what is the big deal? What is the point of including it? For me, the reason is simple. It is about the beauty of the game. Because even if it only happens in one game out of one hundred (to be honest, all the games I have played do not come close to a hundred, even when added up with other people’s recorded games that I have studied) it is bound to happen sooner or later, and when it does happen, it is all the more satisfying. It is like that perfect Queen sacrifice in Chess. It happens in maybe one game out of hundreds, but every fan of the game experiences a feeling of wonder when it does happen.
And it adds depth to the game. A layer beyond the superficial—a step above the norm.
In conclusion, then, I suggest that Burroughs’ Jetan rules should be amended in the following way (added text in italics):
“The Princess may not move onto a threatened square, nor may a player move another piece in such a way that, after the move is completed, that player’s princess is under threat from an opposing piece, even if the move would otherwise win or draw the game. The Princess may not capture an opposing piece.”
In my book Jetan: The Martian Chess of Edgar Rice Burroughs, I divided the rule for the Princess under threat into two segments (these being identical for Jetan and Thuria Jetan). The first reads thus: “A piece may never move in such a way that, by the execution of such a move, its own princess is put in direct threat from an opponent piece [...], even if that move would otherwise win or draw the game.” And the second: “[The Princess] must not end its move on a square threatened by an enemy piece. When in direct threat from an opponent piece, the princess must move away (if possible), unless the threat can be voided in some other way or unless the opponent princess is already under threat.”
A Game of Thuria Jetan
[The rules of regular Jetan are given in AG19 and the rules of the smaller Thuria Jetan (originally referred to as "Chessboard Jetan") are in AG22. The Thuria Jetan rules should be supplemented with Fredrik Ekman's Jetan clarification, given above. ~ Editor]
The following game of Thuria Jetan was played between Kerry Handscomb (Black) and Fredrik Ekman (Orange). The majority was played over a video link on 23 April 2022; the last few moves were played out over e-mail in the ensuing weeks. The game was played with the optional rule that the capture of a Chief with a piece other than the other Chief is a “minor win.”
Abbreviations: Th – Thoat, Wa – Warrior, Pt – Panthan, Dw – Dwar, Fl – Flier, Ch – Chief, Pr – Princess, + – Princess threatened, e – escape, c – Chief taken, minor win
And it adds depth to the game. A layer beyond the superficial—a step above the norm.
In conclusion, then, I suggest that Burroughs’ Jetan rules should be amended in the following way (added text in italics):
“The Princess may not move onto a threatened square, nor may a player move another piece in such a way that, after the move is completed, that player’s princess is under threat from an opposing piece, even if the move would otherwise win or draw the game. The Princess may not capture an opposing piece.”
In my book Jetan: The Martian Chess of Edgar Rice Burroughs, I divided the rule for the Princess under threat into two segments (these being identical for Jetan and Thuria Jetan). The first reads thus: “A piece may never move in such a way that, by the execution of such a move, its own princess is put in direct threat from an opponent piece [...], even if that move would otherwise win or draw the game.” And the second: “[The Princess] must not end its move on a square threatened by an enemy piece. When in direct threat from an opponent piece, the princess must move away (if possible), unless the threat can be voided in some other way or unless the opponent princess is already under threat.”
A Game of Thuria Jetan
[The rules of regular Jetan are given in AG19 and the rules of the smaller Thuria Jetan (originally referred to as "Chessboard Jetan") are in AG22. The Thuria Jetan rules should be supplemented with Fredrik Ekman's Jetan clarification, given above. ~ Editor]
The following game of Thuria Jetan was played between Kerry Handscomb (Black) and Fredrik Ekman (Orange). The majority was played over a video link on 23 April 2022; the last few moves were played out over e-mail in the ensuing weeks. The game was played with the optional rule that the capture of a Chief with a piece other than the other Chief is a “minor win.”
Abbreviations: Th – Thoat, Wa – Warrior, Pt – Panthan, Dw – Dwar, Fl – Flier, Ch – Chief, Pr – Princess, + – Princess threatened, e – escape, c – Chief taken, minor win
1.PtB2–C3 PtF7–E6, 2.Wa–B3 PtG7–G6 3.PtG2–F3 Th–F6, 4.Wa–G3 PtG6–F5, 5.PtC2–D3 PtB7–B6, 6.PtF2–E3 Pt–C5, 7.Fl–F2 Th–C6, 8.PtD3–C4 PtD7–D6, 9.Fl–C2 (Positioning of the Fliers is crucial in Thuria Jetan. Black’s choice to place them on C2 and F2 gives them good coverage of half the game board, with a view to attack Chief or Princess in the future. Orange, on the other hand, creates a “terror balance” over most of rank 5 by allowing his Fliers to remain in their initial positions. Thus, no Flier can make an aggressive move without risking an immediate trade. See Figure 4.)
9....Pt×C4, 10.Pt×C4 Pt–B6, 11.Pt–C3 PtE6–D5, 12.PtE2–D3 PtE7–E6, 13.PtC3–B4 PtD5×C4, 14.PtD3×C4 Pt–A6, 15.Th–C3 Wa–B6? (This opens for a triple fork after Black’s next move, which will force orange to retreat with his Thoat, causing a tempo loss, and to trade a Warrior for a Panthan. Both are weak pieces, but the Warrior is usually regarded as the stronger in traditional Jetan, and this difference should be emphasized in the Thuria Jetan endgame. See Figure 5.)
16.PtB4–B5 Pt×B5, 17.Pt×B5 Th–B8, 18.Pt×B6 Dw×B6? (Orange exposes a power piece without adequate backup, allowing Black to chase it around and finally trade it advantageously for a Thoat.) 19.Th–B5! Dw–A6!?, 20.Wa–A4 Dw–C5, 21.Th×C5 Pt×C5, 22.PtF3–F4 Ch–C6!? (Black now has a considerable advantage, with much better developed pieces and a slight material advantage. Orange, however, has control of the centre, which will turn out to be crucial. At this point, Orange would have been wiser in developing some more of his pieces, instead of throwing the Chief into the fray, to be chased around the board for a bit. See Figure 6.)
23.Fl–D3 Ch–B4?, 24.Fl–C3 Ch–A5, 25.Dw–B3 Ch–C7, 26.Fl–B6 Ch–D7, 27.Ch–C3 Th–C6, 28.Fl–A6 Ch–D6, 29.Fl–A3 Ch–C7, 30.Ch–D3 Pt–B4 (Forces a trade of Panthan and Thoat for black Dwar; this should in theory be fairly equal, but black gives up some of his command of the centre.) 31.Dw×B4 Th×B4, 32.Fl×B4 Ch–B6, 33.Wa–B5 Pt–D5, 34.Fl–C3! Ch–C7, 35.Fl×F6 Ch–E6, 36.Pt×F5!? (This is perhaps the game’s turning point. It would have been more aggressive, and possibly better, for Black to protect his Flier with either Warrior or Thoat. See Figure 7.)
36....Fl×F5, 37.Fl–C3 Pt–E4!, 38.Ch–B4 Fl–C5, 39.Ch–A5 Pt×E3, 40.Wa×E3 Ch–E4, 41.Ch–C7(+) Pr–H6(e) (Escape is necessary at this point, as Black will otherwise catch up, e.g. 41. ... Pr–F7, 42. Ch–E7(+) Pr–H5, 43. Ch–H6(+) and Orange is forced to escape into a more vulnerable position. See Figure 8.)
42.Fl–D4? (Not a very good move, since the Warrior is lost anyway. This move gives Orange two options. 42....Fl–B4(+) inevitably leads to a minor win (or a draw, if the optional rule about minor win is not in force), since he forks Black’s Chief and Princess and will go on to capture Chief after the Princess has escaped. The other option is to play 42....Fl×D4, 43.Wa×D4 Ch–E2(+), 44.Pr–A7(e) Ch×D4, which wins Warrior. The order is important, or Orange will lose tempo and his Chief will be left behind on second rank. In this line, Orange can look forward to a long and complicated endgame where Black has a material advantage, but two of Black’s pieces are cut off from the main force and initially of little use.) 42....Fl–B4(+), 43.Pr–A8(e) Fl×C7(c) Orange wins. ◾️
References
Header image: Edgar Rice Burroughs (1922). The Chessmen of Mars. A. C. McClug. [front cover], painted by J. Allen St. John.
Header image: Edgar Rice Burroughs (1922). The Chessmen of Mars. A. C. McClug. [front cover], painted by J. Allen St. John.
- Edgar Rice Burroughs, The Chessmen of Mars, Gutenberg edition, Appendix (in the Gutenberg e-text, the Appendix is appended to the end of Chapter 22, rather than as a separate segment)
- Fredrik Ekman, Jetan: The Martian Chess of Edgar Rice Burroughs, published July 2022, McFarland
- FIDE Laws of Chess, adopted at the 88th FIDE Congress at Goynuk, Antalya, Turkey, in force from 1 January 2018 (paragraph 1.4.1)
- George Fergus, “Jetan (Martian Chess)”, The Gamesman #5, The Games Bureau, 1970 (the article was first published in The Gamesman #1, but reprinted in #5 along with a new appendix; the discussion referenced here is from the appendix)
- Taylor Kingston, “Is There Chess on Mars?," 1999
- Edgar Rice Burroughs & Fredrik Ekman, “The Rules of Jetan, or Martian Chess," edited 2019