Contested Rules Discussion

Although most of the chu shogi rules are quite clear, the reach of the JCSA during this millenium has caused disruption with their unilateral and unsupported decisions. In this post, I will outline what the JCSA currently implements, as well as how chu shogi was played for centuries before.

Promotion. 

• Shōwa. Pawns and go-betweens can promote on the 12th rank on a non-capture. This makes sense, because both these pieces can prevent lion bridge capture if promotion is deferred.
• JCSA. Pawns and lances can promote on the 12th rank on a non-capture, when promotion was previously deferred. The reason cited for allowing lances this ability stems from modern shogi, and that lances cannot move backward. Lances have no reason to defer promotion, so failure to immediately promote should be punished. They decided that go-betweens shouldn't be able to promote this way, since they can move backwards.
• Early Years. Only pawns had the ability to make a late promotion on the 12th rank.

Repetition.

• Traditional. There were never any specific points mentioned, so it must have been considered common sense to the early players of chu shogi, but the repetition rule made clear that a defending player is never at fault for a repetition, but rather the attacking player. So any single repetition by a clear lone attacking player is illegal. Attacking the enemy king is considered a higher level of attack, so a player whose king is attacked is always allowed to repeat on the next move.
• JCSA. Again egregiously harkening back to modern shogi, they mixed the modern shogi repetition rule with the old rule to create a monstrous and unsatisfactory hybrid that is perhaps worse than either of the two rules alone. It states that any position 4 times on the board is illegal, where the attacking player is at fault if the other player has only defended. The main problem with this rule is that the JCSA considers a player to be attacking is any of his moves in the sequence attack any enemy piece, even incidentally, so a true defender has no proper scope to defend.

Lion bridge capture (sole defender). Capturing first a pawn or go-between, then the lion which only it was defending.

• Traditional. There is no clear old text that indicates how this was handled.
• JCSA. Even though it wouldn't result in a trade of lions, the preservation of which is the main reason for the special lion rules, they insist that a lion cannot capture a non-adjacent defended lion - taking account only before the move is played - even if its only defender is a pawn or go-between that can be immediately taken by a lion.
• Dissenting view. There is also an argument that because it indeed does not result in a trade of lions, capturing twice, first the sole lion's defender (pawn or go-between) and then the lion, should be allowed.

Draw rule.

• There has never, in any official or generally understood capacity, been any rule implemented that would decide a game as drawn independently from a decision of the players.
• Existing local rule. If there are 199 consecutive moves played, without any capture and without any promotion, the game is automatically drawn.

I agree with your 'dissenting view'; HaChu also plays according to that rule. It absolutely makes no sense to forbid this, as, like you say, there is no Lion trading if there is no recapture. So the JCSA rule makes no sense. And the rulses are designed to just prevent trading, doing their utmost to minimize the impact of that. The explicit mention of the 'hidden protector' example in some of the Edo descriptions IMO is meant to indicate that the matter of 'protection' should be judged after the capture, rather than before it.

I am curious about your 'Early years' remark. What evidence are you referring to? Are there tsume problems that only have solutions when such promotion is allowed? (BTW, 1700 doesn't really sound as 'early' to me. It seems Chu Shogi was first mentioned around 1350 BC.)

The issue of 12th-rank promotion of GB seems moot to me: After entering the zone with a deferral that 12th-rank is still 3 (usually heavily defended) squares away, while moving back and forth only requires 2 moves, and produces the Elephant in a more active location. This in addition to the fact that it would be extremely rare you need the GB to go to a location where a +GB could act as a capture bridge. I know of one Edo tsume problem where this happens with a Pawn, but that is obviously a constructed position. So it surprises me that there even would be a rule (traditional or not) for something that virtually never happens.

To be clear, it is illegal for a lion to capture a sole non-pawn/non-go-between defender, then capture the opposing lion, correct?

On the contrary, that is perfectly legal, without argument. 

Could you please specify a source, you are referring?

Also I'm curious, what the JCSA says about the "hidden protector"? Does it actually state that a "hidden protector" doesn't protect the Lion?

Maybe JCSA covers both pre- and post- situations, i.e. the "protection" of Lion is considered in both before move and after move cases?

The JCSA accepts that a lion may be protected by a "hidden protector". Due to the existence of old tsume problems, where this protection is treated as valid, there really is no way to argue against it. This is contradictory in logic to their stance on double-capture of a lion with pawn or go-between.

No, this doesn't come in cotradictory.

The statement about the "hidden protector" states the rule for case of hidden protector, and the statement about protection status of Lion "before the move" states, that the sole pawn/GB defender disallows the Lion capture.

Actually that comes to the situation when the JCSA rules determine both pre- and post-move "protection status" of Lion. In both cases when Lion is protected either before or after move it is considered as protected.

The another thing is, that as you said, "There is no clear old text that indicates how this [bridge capture] was handled", so JCSA has no historical ground for estanblishing this rule about Lion's pre-move protection status.

I would be happy if I could get any historical Chu Shogi documents.

Does anybody have any scans of old texts related to Chu Shogi and/or other large shogi variants?

For example Shōgi Rokushu no Zushiki
https://en.wikipedia.org/wiki/Sh%C5%8Dgi_Zushiki

(c. 1703) There are also tsume problems, but these are just the rule-related parts. It only mentions delayed promotion for pawns. 

That's good.

Can I get a link to it to download or review the full document/documents, please?

https://dl.ndl.go.jp/pid/1869566/1/121

It's a cool site with all sorts of old texts.

Thank you very much!

That's exactly what I needed