Tenjiku Shogi

Tenjiku Shogi is one of the wildest Chess variants ever designed, of which records have been preserved since medieval times. It is a derivative of Chu Shogi, which at that time was the most popular form of Chess in Japan. It added a number of weird but powerful pieces to Chu Shogi, expanding the board from 12x12 to 16x16 to place them. But due to the destructive nature of the new pieces, games of Tenjiku Shogi tend to be shorter than those of Chu Shogi, despite the larger board size.

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Setup

Pieces

The move of pieces from the initial setup is already given in Betza notation above, and should also be clear from the mnemonic piece glyphs in the diagram. The move of piece types that can only be obtained through promotion is given in the rules section. Some pieces that move in special ways are discussed below

Fire Demon

The Fire Demon burns all enemies standing on any of the eight squares next to the one it stands on (as opposed to: moves through). It does this both actively, after it moved, and passively, when an opponent's move lands next to it. The latter has priority: if one Fire demon lands next to another, the moving Demon gets burned, (before it burns anything else) and the stationary one survives. So approaching a Fire Demon is always suicide. (What you capture with such a move will disappear too, though.) Fire Demons can be captured by pieces that exactly land on them, though, without any ill effects on the moving piece. As an alternative to sliding, a Fire Demon can make an 'area move': upto 3 King steps in independently chosen directions. It must stop at the first capture, however, and burning only takes place after its last step. When a Water Buffalo promotes to Fire Demon, all adjacent enemy pieces are immediately burned.

Jumping sliders

The Rook General, Bishop General, and Great General move as Rook, Bishop, and Queen, respectively. The Vice General can also move like a Bishop. But when capturing, all these Generals can jump over an arbitrarily large number of other pieces. They cannot always jump over each other, however, but only over lower-ranked jumpers. The ranking is
4. King and Crown Prince
3. (highest) Great General
2. Vice General
1. Rook and Bishop General
0. (lowest) other pieces
But they can capture each other irrespective of rank, even when jumping something else. The Vice General can also make upto 3 King steps, arbitrarily changing direction between them. These steps cannot jump, and must stop after making a capture ('area move').

Lion and Lion Hawk

The Lion and Lion Hawk are double movers: they can make upto 2 King steps per turn, changing direction between them, even when this returns them to their starting square. They can make the first step as jump, when they choose to do so. So each of them can:

• Jump directly to any square in the 5x5 area surrounding it,
• Annihilate any opponent standing next to it, without moving (formally one step, and then a step back),
• Annihilate any opponent standing next to it, moving on to an empty square next to that ('hit and run'),
• Annihilate any opponent standing next to it, and normally capture an opponent standing next to that ('double capture'),
• Stay in place without capturing anything if one of the neighboring squares is empty (effectively passing a turn)

Free Eagle

The Free Eagle can move as a Queen, but as an alternative can make two diagonal steps, in independently chosen directions, even when this makes it return to its starting square. It can make the first step as jump, when it chooses to do so. So it can:

• Jump directly to any square in the second square in any direction,
• Annihilate any opponent standing diagonally next to it, without moving (formally one step, and then a step back),
• Annihilate any opponent standing diagonally next to it, moving on to an empty square diagonally next to that ('hit and run'),
• Annihilate any opponent standing diagonally next to it, and normally capture an opponent standing diagonally next to that ('double capture'),
• Stay in place without capturing anything if one of the diagonally neighboring squares is empty (effectively passing a turn)

Tetrarchs

The Tetrarchs is a sliding piece that skips the first square in any direction, totally ignoring (and not affecting) what is on it. It can end maximally 3 squares away from its starting square sideway, but can slide arbtrarily far in all other 6 directions. Like any slider it must stop after a capture, or before hitting a friendly piece. Alternatively the Tetrarchs can annihilate any opponent next to it, without moving.

Soaring Eagle, Horned Falcon

Eagle and Falcon move as Queen, except that in some directions they do not slide, but have a 'stinging' move, which can:

• Move to the first or jump to the second square,
• Jump to the second square, annihilating an opponent on the first square,
• Annihilate an opponent on the first square without moving (formally one step, and then a step back),
• When the first square is empty, move there and step back (effectively passing the turn).

Crown Prince

The Drunk Elephant promotes to Crown Prince, which basically is a second King. When you have both King and Crown Prince in play, you can afford one of those to be captured or burnt. Only when you are left entirely without royals the opponent wins.

Knight and Pawn

The Knight and Pawn occur in the Shogi version, the Knight having only is two forward-most moves, and the Pawn both moving and capturing straight ahead.

Rules

Goal

The game is won by capturing all the opponent's royal pieces, or burning them with a Fire Demon (be it in your own turn or in the opponent's). Royal are King and Crown Prince.

Promotion

The last 5 ranks of the board are the promotion zone. Not only Pawns can promote, but almost any piece can. There is no choice for what they promote to, however, for each piece type the promoted type is predefined. Promotable pieces can optionally promote at the end of their turn when they enter the promotion zone. (I.e. start outside it, end within it.) They can also optionally promote when they start their move inside the promotion zone and capture something.

Many pieces promote to a type already on the board initially. But in that case it would be an unpromotable version of that piece, as pieces can only promote once, and then will keep that form for the rest of the game (or until captured or burnt).

The Dog, Lance, Reverse Chariot, Side Mover, Vertical Mover, Blind Tiger and Chariot Soldier promote to piece types not present initially. The pieces promote as follows:

King, Fire Demon, Great General, Vice General, Lion Hawk, and Free Eagle do not promote.

Repetition

The historic sources mention that repetition is forbidden, but do not elaborate on which side carries the burden to avoid it. It is likely that you could not win by perpetually checking your opponent, and that the burden to deviate was thus upon the checker, like in all Asian variants. The modern interpretation of this rule is that evading a perpetual chase, with moves that do not attack anythinging should also be always allowed, so that the chaser must deviate, and that repeats reached without either side attacking anything should be draws.

Lion trading

Despite the fact that Tenjiku Shogi is derived from Chu Shogi, and inherited most of its rules, it does not have any restriction on Lion captures as Chu Shogi has. The reason is that a Lion is not nearly the strongest piece in Tenjiku, so that it makes little sense to preserve it in the game. The Fire Demons really run the show.

Notes

Tenjiku Shogi features all pieces from Chu Shogi, except for the Go Betweens, which are replaced by the Dogs. The Lion, Free King, Horned Falcon and Soaring Eagle, which are 'top of the line' in Chu, not promoting there, can promote to even stronger pieces in Tenjiku Shogi. But otherwise all Chu pieces behave exactly the same in both variants.

The rules governing the captures of the jumping generals by each other are not entirely clear from the historic descriptions. In particular it is not clear whether the rules that forbid lower-ranked generals to jump over higher ranked generals also forbid capturing the latter through jumps. In Chess is it sort of normal that sliders can capture the pieces they cannot jump over. But the historic rules refer to royalty (King, Prince) as having rank 4 in the jump-capture hierarchy. And this can only mean the jumping generals, which all have ranks below 4, cannot jump-capture a King, as the King cannot jump-capture itself, and no one would be interested in jumping over a King if you can instantly decide the game in your advantage by capturing it instead.

In analogy it has been assumed that the jump-capture of non-royal pieces was subject to the same hierarchy as jumping over them. This, however, would allow the Great or Vice General to attack a much more valuable Fire Demon early in the opening, while the Demon is still boxed in, leading to an enormous, likely decisive advantage (of at least a Free King) for the starting player.

Rules that allowed jump-capturing of higher-ranked generals have also been tried, after it turned out that forbidding these captures made the game unplayable. But these rules then also allowed jump-capturing of royalty, which opened the possibility for early suffocation mates, again making the initial position tactically non-quiet, and leading for an unfair first-move advantage.

The rules initially described here (not restricting what you can jump-capture, except royalty) did not have this problem, as any jumping general attacking the Fire Demon would place itself under attack by the 'shield' of jumping generals standing directly in front of the Demon, which all can move radially away from the latter. The chances that this placement (or the fact that the Vice General moves diagonally rather than orthogonally) is only a coincidence are rather slim, so the initial setup seems designed for the rule that jump-capture of generals by each other is possible irrespective of their rank.

However, in 2022, during a discussion between A. M. DeWitt and H. G. Muller, the latter realized that the evidence for not allowing the jump-capture of royals was flimsy at best and nonexistant at worst. The reasoning behind the restriction against the jump-capture of royalty mainly came down to a smothered mate threat after making way for the Vice General on the first move (or the right-side Bishop General after two moves), which resulted in an unfair first-move advantage. However, the restriction against jumping over royalty applies to both enemy royals and friendly royals, and the historical sources mention this but provide no further comments on it. Furthermore, there are plenty of options for defending against such a threat. The best one is to move the left Soaring Eagle outward, defending against both mate threats, but advancing the left Knight Pawn also works (putting more defence on the Vice General's mate threat, at the cost of not defending against the Bishop General's mate threat). If Sente runs out of steam attempting the smothered mate threat, Gote can follow up with the same threat.

Last revised by H. G. Muller.