Author Topic: Tenjiku Shogi opening theory  (Read 85 times)

HGMuller

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Tenjiku Shogi opening theory
« on: March 07, 2018, 10:41:57 am »
The historic Japanes game Tenjiku Shogi is one of the most violent Chess games ever conceived. It features 'Fire Demons', which do not only capture what is on the square they land, but 'burn' every enemy on the 8 adjacent squares as well. Somewhat like Atomic Chess, except that they do not explode themselves (or any friendly piece), so they can keep doing it turn after turn. And it even does it in the opponent's turn as well; moves that land adjacent to an enemy Fire Demon make the moved piece evaporate without a trace. (Even a Fire Demon itself  evaporates this way, without burning anything.)

Apart from that the Fire Demon is an enormously mobile piece. It moves as a Queen, except along one of the orthogonals. (There is some controversy whether this would be sideway or vertical.) And in addition it can make up to 3 King steps, allowing it to sneak through holes in the enemy lines and around corners. (But must stop on a capture, i.e. when it reaches a square that was occupied.) This gives it 30 extra move targets not reachable by the Queen moves, many of them more difficult to block, as they can be reached through more than one path.

Unlike most Shogi variants, the opening phase of Tenjiku Shogi is extremely tactical. At least with the rules that modern players use, where another class of exceptional pieces (the 'jumping generals) can deliver check. (Whether the historic rules allowed this is also controversial.) These pieces can jump over arbitrary many other pieces when capturing, so they are practically unblockable (except by each other). The problem is that in the initial position the King is completely smothered, so any (safe) check would be a mate. So not to get checkmated is a major problem, starting from move 1: the most popular opening move immediately threatens mat in 1.

No information has survived from historic times about strategy and opening theory. The historic manuscripts only contain a rule description. So modern players have to discover the critical opening theory all by themselves. I wonder if this forum would be a good place to discuss Tenjiku Shogi opening theory.

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HGMuller

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Re: Tenjiku Shogi opening theory
« Reply #1 on: March 14, 2018, 03:35:44 am »
Let me start with a diagram of the initial position, using 'mnemonic' piece icons. This makes the way most pieces move trivially recognizable from their pictogram: virtually all pieces only slide along principal rays (like a Queen), with infinite range, or just one or two steps. (Or not at all.) Pieces that only step are depicted as a small square, with 'bites' taken out of it in the directions they cannot step. If they move more than a single step in a certain direction, they bulge out of that square. A radial line then indicates infinite range, otherwise the range was two.



Only few pieces have moves more complex than can be indicated by this system, and have special icons. Of notable importance are the (2x) 6 pieces depicted as circles. These are the 'jumping generals' (Great General, Vice General, Rook General and Bishop General), which can jump over an arbitrary number of pieces when capturing. Otherwise their move is as their name (and the radial striping pattern on their icon) suggests. The VG in addition can also make up to 3 King steps in arbitrary directions. The sliding capture moves of these generals cannot be blocked by normal pieces (they can block each other according to some hierarchy, however). So they pose a very large danger to the King, for inflicting a smothered mate.

The dominant piece is the Fire Demon, depicted as a candle flame. It 'burns' all adjacent enemy pieces, and thus can capture up to 8 victims in a single move. In 21st-Century Tenjiku it moves like a Queen except sideways, in addition to be able to take up to 3 independently chosen King steps. Tenjiku openings start with an 'aireal fight', where the jumping generals and Fire Demons roam the board, the other pieces being hardly touched at all. Unlike in Chess, multiple moves with the same piece is common practice.

The most popular opening move is 1. P-j6, to open a hole for the VG to move out. (We use standard board coordinates here, where a1 is the lower-left corner.) This immediately threatens a smothered mate through 2. VG-o10. The Kirin on j15 is the only piece adjacent to the King that can be moved in the initial position, to create some breathing space. But as this happens to be on the check diagonal, it would not prevent the mate. So black must cover the checking square o10 to prevent the mate. There are only two moves that do this: 1... SE-n11 and 1... P-o11.

Now 1... P-o11 does not work, and gets black mated in 3 anyway: 2. VG-n9 {now threatens mate on p9} SE-n11 {the only way to cover p9} 3. VG-p9 SExp9 4. BGxp9#. So 1... SE-n11 is a forced move. This is then usually followed by 2. BG-i6 to mount an attack on the SE that is critical in preventing the mate. (Threat: 3. BGxn11 {check} Pxn11 {only evasion} 4. VG-011#.) There are several ways to make sure the protection of o11 can be maintained. For one, the Soaring Eagle protecting it can be moves out of the BG's attack, 2... SE-p11 or 2... SE-p9. In addition, the SE can be protected by a Water Buffalo by moving up the intervening Pawn, 2... P-m11, so that after 3. BGxn11 WBxn11 the square o10 stays protected (by the WB).

Before discussing the merits of each of these defenses, we note that white's first two moves can be mate threats, which can be countered only by comparatively passive moves, which don't do much for black's development. For white, however, this has cleared a path for its Fire Demon to develop. E.g. through 3. FD-k6 (the 'Quick Attack'). As the Fire Demon has an enormous destructive potential, its early development can give a huge advantage. Black's moves for preventing the mate did not help develop its FD in any way. So it seems white has a huge initial-move advantage.

The Quick Attack

This is largely illusory, however. Because on the other wing the situation is still just as it was initially. So once the mate-in-1 and checks-only mate threats are dealt with, black can simply mirror white's play, making his own mate threats during development of his Demon, forcing some passive defensive moves on white: 3... P-g11 4. SE-c6 BG-h11 5. P-d6 FD-f11. This restores the symmetry, and thus keeps the white advantage limited to the original one of having the move.
« Last Edit: March 14, 2018, 04:42:58 am by HGMuller »

chilipepper

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Re: Tenjiku Shogi opening theory
« Reply #2 on: March 14, 2018, 07:53:35 pm »
(There is some controversy whether this would be sideway or vertical.)

Do you mean it's not clear what the original rules are? I wonder if the rules can be "backwards-engineered" by learning which rule creates the better play. Of course, that would only work if the game was already played and studied enough so that it was already optimized for the most tactical style of play (assuming that was even the goal).

So modern players have to discover the critical opening theory all by themselves.

I suppose this is true based on the premise that it's played less now, than it was in the past, and that nobody has analyzed it yet with computers (which I would assume is true)?

Thanks for sharing this info. Interesting! :)
the "chilipepper"👹

HGMuller

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Re: Tenjiku Shogi opening theory
« Reply #3 on: March 15, 2018, 05:07:04 am »
Indeed, the historic rules are not very precisely defined. There are only two historic manuscripts that mention the game, and I don't have access to the raw data. (Which might not be very helpful anyway, as it would be in archaic Japanese, in non-machine-readable form, and I don't read Japanese at all.) The controversy on the direction of the Demon move might be because of a discrepancy between the verbal discription and a drawing in the same manuscript.

People have been trying computer analysis for decades, but only since last year I have a program that can search deep enough to make this meaningful. Much of what I plan to post here is based on analysis with this program. (At the moment set to use the rules commonly used by modern players.)

Rule unclarities that would hugely affect the game are:
1) Whether the jumping generals are allowed to capture the generals they are not allowed to jump over. (This seems standard behavior in Chess; e.g. Rooks cannot jump over enemy pieces, but they have no problem capturing them. So it is not clear why this has become an issue.)
2) Whether jumping generals are allowed to capture the King. The rules mention the King in the hierarchy of pieces that could not be jumped over, but who would want to jump over a King if he could capture it? It would become a totally different game if the generals could not inflict smothered mates.
3) Wether the Fire Demon moves along files or along ranks. The forward forking power when it moves along files (in addition to diagonally) is extrordinary large, giving an unfair advantage to the side that manages to develop its Demon first. (I.e. huge first-move advantage.)
4) Whether a Water Buffalo, when it promotes to Fire Demon, already burns away the adjacent enemies during its promotion move. Modern rules assume this is not the case, for no clear reason, and at the price of rule inconsistency for what happens later. (Pieces would remain standing next to the Demon, while new pieces landing there would evaporate.) With instant burning the Water Buffalo would become 'nuclear tipped', and a much more dangerous piece, as you could just run it into a dense crowd in the enemy camp to annihilate 4 or 5 Queen-class opponents, not caring much about the recapture.

HGMuller

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Re: Tenjiku Shogi opening theory
« Reply #4 on: March 31, 2018, 01:16:47 pm »
Demon attack spots

Before discussing actual opening lines, let us take a look to some general principles. E.g. why is it so important and advantageous to develop your Fire Demon quickly?

The initial position has a fair number of weak spots for Fire-Demon attack. The Pawns on c12 and n12 are protected in the normal sense, but not protected against capture by a Fire Demon, which would burn all protectors with it. (This sometimes also works the other way around; a piece can be unprotected because distant sliding protectors are blocked by an adjacent piece, and a Demon would burn that adjacent piece.) These Pawns can be protected by moving Bb15 or Bo15, respectively.

All other Pawns are protected against Demon capture. As a Demon is 'priceless' (it would win against almost any combination of non-Demon material), this seems to make the starting position resistant to Demon attack, no matter how much material there was behind the Pawn that would be burned together with it; recapturing the Demon would always be enough compensation. There are tactical complications, however. The Rook Generals aim at the opposing Demons, but block each other from reaching those. If, however, one of the Rook Generals gets burned, this activates the RG attack on the Demon behind it, which could now be traded for a single RG. So after the initial burn you get immediately in a position where both Demons are under attack. This doesn't help if the defending player can use his Demon to capture yours, and this will move him out of the RG's path. But after a capture/burn on the Pawns in the RG file (g12 or j12), the RG does not only attack the defending Demon, but it protects its own. So whether you recapture FD x FD, or recapture the FD with another piece and leave your FD where it is, in both cases you will get RG x FD. Of course you can then recapture that RG, but it means you get only a single RG, while the initial burn might have destroyed three of your jumping generals (GG + RG + BG or VG + RG + BG). A very bad deal.

A similar case occurs on a Demon capture/burn on the Pawn in front of the Vice General (h12). This burns GG + VG + RG, the latter exposing the FD to RG capture, while the attacking Demon is protected to its own GG. This would thus gain a VG + RG. The common method to protect yourself against capture on g12, h12 or j12 is trading the RG which is going to get burnt for the opposing RG, even if the latter resides next to a Demon so that it evaporates as a side effect (and thus loses you a tempo). Then your Demon would not get under attack from the initial burn, so you can safely recapture the attacking Demon with another piece, (e.g. LH or FE), even if it is protected.

Even after such a defensive RG trade, a capture/burn on h12 can still be attractive, because lacking a GG early in the game, when the King is still suffocated amongst its own pieces, can cause big problems. The surviving GG could check from i4, after the VG normally standing there has evacuated that square. Which it often can do with a check. If that is the case there is burning of the GG causes an immediate mate-in-2 threat. Making an 'air hole' for the King on j15 by moving away the Kirin often does not help, because the GG, after checking on i4, can diagonally check on o10, covering both the original King square and the escape square. Or because a RG can assist to cover it. In that case the only way to prevent the mate would be to make sure you can burn a checking GG or RG on i4, for which your Demon has to come out. So that you have to recapture after an h12 burn with a Demon to not get mated. After which that Demon is again traded for a single GG.

Even in if the defending side does not have to recapture your protected Demon after burning the opponent's GG + VG, the latter can be an attractive deal. Provided that you can force the opponent to sac its Demon back. Burning a checking GG on i4 might be the only way to prevent checkmate after he loses the ability to block it. And you might be able to reduce the damage done by that to a single GG, or GG plus one other jumping general, while your original burn destroyed more generals.

So there are in fact many places where you could slam a Demon into the Pawn wall to gain significant material. And a Demon has great forking power, with its three forward-directed sliding moves. One such sliding threat might be blockable by moving up a Pawn, but if the Demon attacks multiple vulnarable spots there is just no defense. If the Demon can approach your Pawn rank to within the range of its area move, he even attacks 7 Pawns at once, most of those through multiple paths (so that blocking is out of the question). Manoeuvring with the Demon to get a good shot at a profitable burn is therefore the major theme of all openings in Tenjiku Shogi.