Courier Chess, Part II: Modern Variations

UPDATE 14 Feb 2022: Added Modern Courier Chess and Reformed Courier Chess, and updated my recommendations and some other text. Watch out for these games in the next Ai Ai release!


Modern Takes on Wider Chess

In my previous post on Courier Chess, we took a look at the classic 12th century game of extended 12×8 Chess, which maintained a player base for hundreds of years before finally being overcome by the modern game. Courier is perhaps a bit deliberately paced compared to the 8×8 game we’re all familiar with, but I maintain that it has a great deal of charm and definite strategic interest.

We also met Courier Spiel, a 19th-century revamp of the classic game that added modern touches like a full-power Queen and double-stepping Pawns:

Note that in the Ai Ai implementation, Courier-Spiel uses more standard promotion rules — Pawns must promote on the last rank to any previously-captured piece of the same colour — rather than the strange triple-backward-hopping rules associated with the historical game. If there is demand I can look into providing the old rules, but frankly I think it makes endgames much slower and more difficult to convert, so I find the modernised promotion rules more enjoyable.

Below I’ll introduce you to a few interesting modern Chess variants that take Courier as a jumping-off point. All of these games are playable in Ai Ai against humans or against the AI. Feel free to give them a try, and let me know in the comments which ones you prefer.

Courier Chess with Alibabas

We’ll start here with a very simple variant — this one is exactly how it sounds: Courier Chess, but with the Alfils swapped for Alibabas. The Alibaba is a compound piece that combines the moves of the Alfil — jumping two squares diagonally — with the Dabbabah, which jumps two squares orthogonally. That gives the piece significantly more power, while still restricting it to a subset of the squares on the board.

I have to say I quite enjoy this simple piece swap; the resulting game is still deliberate and strategic like the original, but the Alibabas are stronger and exert more influence on the game. In the sample game, you can see how they prove very useful in the endgame for Black! I’m a fan of Chess variants with intricate endgame play, and this certainly provides that.

ArchCourier Chess

ArchCourier, invented by Eric Greenwood, is a highly-playable modern take on the Courier experience. Eric went to great trouble to tweak and test the game to ensure the piece mix was suitable and that the initial setup was balanced, and I feel he did a very good job.

Rules-wise the game is easy to grasp — all the familiar pieces from Chess move as in the modern game, including the Queen and Pawns. No castling is allowed. Pawns that reach the far rank must promote to any previously-captured piece of the same colour.

However, four new piece types join the fray in this game that give it a very distinct personality from classic Courier:

  • Centaur: moves as a Knight or a Guard (non-royal King)
  • Squirrel: may jump as a Knight, or jump two squares in any diagonal or orthogonal direction — in other words, it can jump to any square two steps away from its starting point
  • Dragon Horse: moves as a Bishop or steps one square orthogonally
  • Dragon King: moves as a Rook or steps one square diagonally

The Guard parked in front of the King provides useful defensive cover, particularly since there is no castling.

The new pieces are well-suited to this game and to Courier’s distinctive 12×8 board. I’m particularly a fan of the Squirrel, a flexible and fun leaping piece that can crack open some surprising tactical opportunities when used well. The Dragon King and Dragon Horse, which will be familiar to Shogi fans, are helpful additions on this larger board.

Alas, ArchCourier does not seem to have received much attention since its creation, which is unfortunate. I highly recommend it for fans of Courier who want something with a bit more zip, but with no real additional rules overhead to worry about.

Modern Courier Chess

This game was developed by FIDE Master Paul Byway and revealed in the now-defunct magazine Variant Chess in 1992. Modern Courier Chess was an attempt to revitalise the ancient game by modernising the moves and changing up the arrangement of pieces, which Byway felt was awkward in the old game. Byway wrote extensively about the game in many issues of Variant Chess, including many analysed games, making it quite possibly the most well-analysed 12×8 variant of all time. All back issues of Variant Chess are available for free download in PDF format, so do go check out Byway’s excellent articles.

Modern Courier updates the ancient game firstly by upgrading the Pawns to the modern standard, and making the Queen a modern one as well. The Elephants are upgraded to Alibabas, and the Fool/Sage pairing of the original game is simplified down to two Ferzes, though each Ferz is granted the ability to make a non-capturing Alibaba leap on their first move only. Castling is not available; instead, an unmoved King that isn’t in check may make a double move in any direction as their first move.

The result is a very appealing variant with ample room for deliberate, strategic play, given that the pieces are kept at a relatively low level of power. If one already knows Courier Chess, then this version is very easy to pick up, as the rule changes are relatively small. Finally, the extensive analysis by Paul Byway ensured that this game is very well-balanced, and a huge variety of opening lines are playable.

Modern Courier Chess has just been added to Ai Ai (as of the time of writing in mid February 2022), so once the next release is available I urge you to give it a try. I personally prefer some of the other options a bit more, as I find the overabundance of diagonal pieces in MCC a bit off-putting, but the game is undeniably well-constructed and highly enjoyable.

Reformed Courier-Spiel

Reformed Courier-Spiel, invented by Clément Begnis in 2011, is a reaction of sorts to Modern Courier Chess. On this website Begnis recounts some of his objections to Byway’s approach to the 12×8 game, and outlines his reasoning for taking Albers’ 1821 formulation Courier-Spiel and modernising it. In essence, he keeps the general shape of Albers’ approach but revises the starting position, castling/promotion rules, and changes up the pieces:

In Begnis’ game, the Courier is renamed the Archer, and given the extended Elephant’s move: it may jump 1-2 squares diagonally. The Fool is renamed the Champion, and may move as a King or as a Dabbabah (leaping 2 squares orthogonally). Finally, the Sage is renamed the Paladin, and moves as a King or a Knight (this piece is known elsewhere as the Centaur). The resulting play is very appealing, in my view, providing a nice upgrade in mating power on the board while not turning the game into an overly hectic tactics-fest.

Reformed Courier-Spiel is perhaps best-suited to the player who has some familiarity with Chess variants, as the new moves will be fairly familiar in that context. The Champion’s move is a nice innovation, however, keeping the late-game mating power of the Man while allowing it to develop earlier with the Dabbabah move.

On the whole I find Reformed Courier-Spiel very enjoyable to play, and I highly recommend it to anyone interested in this elongated variants. I place it in roughly same category as ArchCourier Chess, in that it uses modern variant pieces to spice up the old game, but manages to keep the power level contained nonetheless. In fact, in testing I found that Reformed Courier-Spiel games tend to last roughly as long as Modern Courier Chess games, despite the increased power of the pieces. I’ve found that I tended to end up in some quite intricate and technical endgame positions while playing Reformed CS against the AI, which is a great thing for me given my fondness for the endgame in general.

In any case, at the time of writing (mid February 2022), Reformed CS has just been added to Ai Ai, so look out for it in the next release!

Courier de los Combinados

Courier de los Combinados, created by prolific Chess inventor Charles Gilman, is essentially a combination of ancient Courier with Wildebeest Chess, a popular modern variant on an unusual 10×11 board. Wildebeest Chess extended the Royal Game by incorporating new leaping pieces: the Camel, an extended Knight found in the ancient large variant Tamerlane Chess; and the Wildebeest (also known as the Gnu), a combination of Camel and Knight:

Wildebeest Chess (which I’ll cover in a future post) is known for a wide-open style of play, thanks to these long-distance leaping pieces and a fairly empty board compared to standard Chess. Courier de los Combinados goes the opposite direction, packing Courier’s 12×8 board with additional pieces:

Alongside these two Camels and a Wildebeest on each side, the Wazir and Ferz pieces have been doubled up and parked in front of the King, creating an advanced forward line of Pawns. The Alfils are gone entirely, and the Queen is upgraded to its modern power levels. The King may also castle with his Rooks, and Pawns must promote at the last rank to Queen, Wildebeest or Guard.

The play that results is quite interesting; while the initial setup is fairly dense, the long-distance leapers provide some lethal early threats, making the opening surprisingly sharp. In fact, be careful which Pawns you move in the opening, as very quick Wildebeest mates are possible if you open up the wrong squares! Note that in the sample game, an AI vs AI test game, both sides elected to allow the opponent to take a Rook early on; I suspect this is very much not an optimal opening! Clearly I need to do some tweaking to Ai Ai’s engine parameters for this game.

Charles Gilman produced a shocking number of variants during his time on the Chess Variant pages, and was at times criticised for not actually playtesting enough of his games. I can say however that this take on Courier has proven to be quite interesting, and may provide some intriguing challenges for opening theoreticians!

Northern Ecumenical Chess

Here we have another interesting Charles Gilman creation, this time extending Courier’s board to 16×8, or the equivalent of two standard Chess boards laid side-by-side. Northern Ecumenical Chess takes Courier de los Combinados to the next level by adding in compound pieces of the Knight and Camel:

  • Cardinal: moves as a Knight or a Bishop
  • Marshal: moves as a Knight or a Rook
  • Caliph: moves as a Camel or a Bishop
  • Canvasser: moves as a Camel or a Rook

Rules-wise, we have castling in this game (with the Rooks), Pawns may take an initial double step, and must promote to any non-Pawn piece upon reaching the last rank.

I believe this was one of the first games I added to Ai Ai once the Camel compound pieces were available, which tells you something about my opinion of the game. I have a certain fondness for oblong boards in Chess, and going all the way to 16×8 is even more entertaining in my opinion; such boards can be easily constructed by mashing together two standard boards, which is a practical benefit, and the odd shape creates a substantially different feel in play. As you might expect, pieces that can slide horizontally — Rooks, Marshals, Canvassers and Queens — are even more useful here, as they can reposition more easily than the diagonal pieces, which take multiple moves to cross the longer axis of this board. The Knight feels less powerful on a board like this one, given how long it takes to get it to a useful position, but in contrast the Wildebeest is a flexible and dangerous attacker.

All told, I enjoy this variant quite a bit and find it a nice balance between rough-and-tumble tactics and slow-burn positional play. If you fancy experimenting with a very long board and some unusual pieces, I can highly recommend giving this a try.

Other Oblong Oddities: Duke of Rutland’s Chess

As I got into Courier Chess and its variants, I soon discovered that Courier was not the only historical Northern European expanded Chess game on an oblong board. This game was invented by John Manners, the Third Duke of Rutland in 1747, and it managed to have a brief spell of popularity until his death in 1779. The game has languished in obscurity since then, but we still honour the Duke’s creative accomplishment by calling it Duke of Rutland’s Chess.

Rutland’s Chess is an odd game, not just for its unusual board size, but also due to the selection of pieces:

Click on the image of the starting position and you’ll see the strangeness for yourself (note I use the starting setup provided in Jean-Louis Cazaux’s book A World of Chess, rather than the setup on the Chess Variant Pages which is the mirror image of this one). First, we have four Bishops instead of two, and three Knights instead of two, which introduces an unusual imbalance between the minor pieces. Second, we have Dragon Kings present — moving as Rook or King — yet we have no Dragon Horses (Bishop or King). Third, we have a Marshal (Rook + Knight), but no Cardinal (Bishop + Knight).

This strange starting army raises a number of questions. Why are two of the Bishops not Dragon Horses instead? Did the Duke not know about them? If he didn’t, one would expect he would have easily extended the Dragon King’s move to the Bishop and reached the same conclusion anyway, but it seems he didn’t. Why the third Knight? We know that the Cardinal and Marshal (Bishop + Knight and Rook + Knight) were known at least since 1617 in Carrera’s Chess, and a Marshal is present here, so why no Cardinal? I find those oddities a bit fascinating; perhaps we may never know why the Duke made these particular design choices.

All that aside, the resulting game is nevertheless quite entertaining. The extended board is deeper than that of Courier Chess, providing more room for manoeuvre. The Pawns in this game have the option of an initial double- or triple-step as their first move, meaning that the deeper board doesn’t particularly bog down the opening. The presence of the modern Queen, Marshal and Dragon King further open things up, providing opportunities for sharp tactical play. After a few plays one can see why the game found a certain following, at least for a brief time; apparently the legendary Philidor was quite the fan of this game.

Modern Manners

As one might expect, Duke John Manners’ unusual game has provoked some interest in the Chess variant community, and various inventors have tried to resolve the imbalances in the original game’s starting position. A simple and effective example is Modern Manners, coming to us from the ever-prolific Charles Gilman.

Modern Manners uses the same board as Rutland’s Chess (though the image in the linked CVP entry shows a 14×8 board instead, for some reason), but alters the starting setup in the most logical way:

Modern Manners replaces the odd third Knight with a Cardinal (Bishop + Knight), and swaps out two Bishops for two Dragon Kings, giving us a logically complete setup and a slightly increased overall power level. As in Rutland’s Chess, Pawns have the option of an initial triple-step forward, and they may promote to any non-Pawn piece upon reaching the last rank.

I highly recommend this game as a modern alternative to Rutland’s Chess; the new setup is easier to understand and use, and the addition of the Cardinal in particular livens up the tactics even further. Of course you should try Rutland’s innovation first, as you may well find its quirkiness to your liking! Personally I feel these simple changes transform the game into a more engaging and more logical game, and yet it retains the wide-open, fast-paced feel of the original, so I prefer this to Rutland’s effort.

Manners Kamil

Charles Gilman didn’t stop there — on the very same CVP entry you can find Manners Kamil, a 16×8 game that adds two Camels and swaps the Cardinal and Marshal for two Wildebeests:

The lengthened board and altered pieces substantially change the feel of this game. The powerful long-distance attacks of the Cardinal and Marshal are replaced with the airborne threat of the Wildebeests, leading to some tricky tactics in the early stages of the game. In fact I’m slightly uncertain as to whether the game is meant to be played on a 16×10 board; the CVP entry is ambiguous, given that the Modern Manners board is shown as 14×8 despite the clear statement in the text that it uses the Rutland Chess board. The Manners Kamil description states that 2 files are added but does not explicitly mention the board’s depth, so perhaps 16×10 should be used instead of 16×8.

In any case, I will experiment more with Manners Kamil on 16×10 and provide the .mgl file in a future release of Ai Ai. For now I do recommend giving this game a try on 16×8 and seeing how you feel about it. The compressed vertical dimension is somewhat compensated by the reduction in long-range pieces, and on the whole the game still feels fairly open. However, I sense that the player best able to develop their Rooks and Dragon Kings may enjoy a good advantage; without them in play, only the Queen can hold sway over the board’s longer axis.

In my admittedly limited test plays thus far, I sense that the 16×10 version may be slightly better. The open playing area is more reminiscent of Modern Manners and its historical predecessor, and the additional two rows give the opening a bit more room to breathe, while also reducing the early mate threats of the Camels and Wildebeests.

Sneak Preview: Giga Rutland Chess

Here’s a quick sneak peek at one of my own creations — Giga Rutland Chess, a huge expansion of the original’s rather sparse starting position:

An entire extra row of pieces is added to each side, which includes types of pieces completely new to Rutland’s Chess:

  • The Phoenix and Kirin, adopted from Chu Shogi
  • Knights and Camels enhanced with additional short-range moves
  • The Hunter (moves forward as a Rook, backward as a Bishop), and the Hawker (moves forward as a Bishop, backward as a Rook)
  • And more besides!

I won’t go into much detail here because the game is still being tested, but my intent has been to provide a denser, more hectic game on the 14×10 board, and while it may be rather too much for some, I find it enjoyable so far. More to come on this game once it’s finalised. I’m currently in the third major revision of this game; the most significant change from the previous version was to remove the Cannon pieces, which I find difficult to manage on large, dense boards, as their tactical threats are hard to spot in that context. More changes may come in the future, but so far this version seems promising!

Alekhine Chess

This game is a bit of a mystery in some ways — despite the name being Alekhine Chess it has nothing to do with the famous Chess player Alekhine. Why is it called Alekhine Chess then, you ask? I have no idea. But that aside, it’s an intense and dramatic variant on a 14×8 board, and a good choice for fans of brutal tactics.

As large variants go, the setup here is pretty simple: all the standard Chess pieces are here, plus an extra Queen, two Marshals, two Cardinals, and an Amazon (Queen + Knight). The presence of all these powerful pieces generates a game of intense tactics; most of the pieces on the board are incredibly mobile, and the Amazon can actually checkmate the enemy King completely on its own, without the help of any other piece!

I must say I was a bit sceptical of this game initially, as the Cardinal, Marshal and Amazon are very common pieces in Chess variants and not that fascinating, and the sheer power density on the board seemed like it might reduce the game to a simplistic slugfest. But in practice, it’s anything but simplistic. The entire game will balance on a knife edge, certainly, and a single blunder could result in a horrendous slaughter, but there’s absolutely room for positional thinking thanks to the large dimensions of the board. As you can see in the GIF, each game of Alekhine is high intensity, and when playing you must get comfortable with being under constant threat at all times! I enjoy this variant a lot, and would be happy to see it gain more traction.

Double Chess

Here we have a game that doesn’t quite fit the mould we’ve established here so far. Double Chess is exactly what it says on the tin: Chess, except doubled! We use a double-length 16×8 board, give each player two full Chess sets for their side (but replace the extra King with a Queen), and off we go:

Now, some may quite rightly take issue with me including this game in a list of Courier-inspired games. Courier, Rutland’s Chess, and the others in this article are full-on extensions of Chess, expanding both the board and the pieces available to each army. Double Chess extends only the board, using only standard pieces. However, in my mind the use of the double board places it in a similar category, if only because of the distinctive feel of playing on these elongated boards. The use of only standard pieces also makes the game extremely easy to play in real life — just buy two cheap tournament Chess sets with those roll-up plastic boards, trim the edges so you can fit the board edges snugly together, plonk your two sets of pieces down, and off you go!

The resulting game is surprisingly different from normal Chess, and of course can run substantially longer. I usually prefer games with new pieces, but this game is one of the few using only the standard army that I find just about as good as the more adventurous designs. Creator David Short also provides some sample games and a fully-commented game to help the beginner, which is fantastic for those looking to give this game a try.

On the whole it’s an excellent game, and well worth your time.

Full Double Chess

Full Double Chess takes the basic idea of Double Chess and extends it, so that the board now includes the compounds of the Knight with the Bishop, Rook and Queen:

Full Double Chess has one immediately obvious deviation from Double Chess — each side has two Kings! Each King can also castle with either the Marshal or Rook on either side, meaning that when implementing this game I had to allow for a huge assortment of possible castling options. Both Kings must be eliminated to win, which is a nice counterbalance to the huge power of the additional Cardinals, Marshals and Amazons on the board. Thanks to the double Kings, the game won’t end immediately after a single blunder — though of course the Amazon could easily checkmate both Kings at once if you’re not careful!

Full Double Chess is quite a fun variation on the oblong Chess theme; the double Kings are an unusual feature that works really well in this context. The additional Knight compound pieces are again not the most exciting pieces, but fit perfectly in this game, and make it easy to introduce this game to someone who may be new to the concept of Chess variants as a whole. I think this game co-exists quite nicely with Double Chess; they play entirely differently and present really divergent takes on the double-board theme. David Short, creator of Double Chess, was rather disparaging of Full Double Chess on the basis of its ‘new fangled’ pieces; however, the added pieces in this game were in fact invented centuries ago, so the only way they could really be ‘new fangled’ is if David is several hundred years old!

My only issue is the name, really. The creator insists the game includes all the compounds of the basic Chess pieces, but we are actually missing Rook + Knight + King and Bishop + Knight + King, which can be seen in Jean-Louis Cazaux’s Very Heavy Chess (more in this game in a future article). In my opinion, a truly ‘Full’ Double Chess perhaps should include those pieces and widen the board even further. Besides that very pedantic gripe, I strongly recommend giving this game a try!

Final Thoughts

I hope you’ve enjoyed these brief introductions to a few games that build on the oblong foundations of the ancient game of Courier Chess. There are more games in this category that I haven’t covered, of course, but I’ve tried to include a good variety of options within Ai Ai that give players some interesting and distinct games of this type.

If you’re new to these types of variants, I’d recommend that you start with the historical games first — Courier Chess, Courier-Spiel and Duke of Rutland’s Chess. These games are very distinct from modern Chess but are easy to pick up and play as a newbie, and they’ll be a nice introduction to the feel of playing on a widened board. From there, you can progress to modern takes on each, with the natural next step from Courier being Reformed Courier-Spiel due to its relationship to Courier-Spiel, and of course Modern Manners is the natural follow-up to Rutland’s Chess. From there, Modern Courier Chess and ArchCourier would be excellent choices.

If you want a modern take that diverges further from the Courier model, Double Chess is an enjoyable and highly accessible double-board game to try out. Alekhine Chess is a good one to try as well, particularly for the tacticians out there. Finally, if you hunger for some new pieces on the longer boards, I can recommend Northern Ecumenical Chess as an enjoyable and balanced double-board game with interesting yet intuitive new pieces.

From here I will move on to some other approaches to large board Chess and give some more comments and reviews on games in these categories. First I plan to cover games that extend the Chess army through compounds of classical pieces, like we saw in Alekhine and Full Double Chess; there are a LOT of games like this however, so I’ll be quite selective in my coverage. I’ll also include some games of mine in this category, which take the compound-piece approach to its logical extreme.

I should mention that in the previous Courier article, I’d promised to provide some detailed commentary on sample games of Courier and Courier-Spiel; unfortunately I have to put this to one side for now, as I did a tonne of work for that post and managed to lose nearly all of it! I do plan to get back to that, but I’ll need to start my analysis again, so it will take some time.

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8 thoughts on “Courier Chess, Part II: Modern Variations

  1. Juan L. says:

    Regarding Courier Chess with Alibabas, the british FIDE Master Paul Byway invented in the 90s Modern Courier Chess, a modernised version of Courier Chess, with Alibabas (deceptivelly and against historical tradition, called “Couriers” by Byway) instead of Elephants. Sage and Fool are each replaced with a Ferz, and a modern Queen replaces the ancient Queen (a Ferz). Queen and King positions are swapped, to appear like in FIDE standard chess. There is no castling, but an unmoved King, when not in check, can optionally do a double move to a vacant square (so, no capture at all allowed), provided that it can be expressed as two legal single moves. An unmoved (and no created by promotion) Ferz can optionally move to a vacant square (no capture at all allowed, too) like an Alibaba. A pawn can promote to any non-royal piece. See, for example: https://www.mayhematics.com/s/modco.htm

    Byway was contributor and editor (autumn 1999-may 2004) of the Variant Chess magazine. All the magazine issues, from 1990 to 2010 can be found here:
    https://www.mayhematics.com/v/v.htm

    In several issues, since the 8th issue (introduction and six commented games) to the very last, can be found commented games, studies (some of them apply to other Courier variants) and puzzles of Modern Courier Chess. Interestingly, Byway argued against introducing too many powerful pieces in his Courier modernization: see, for example, issue 37(2001) (p. 78-79) of Variant Chess, where he criticises Albers’ Courier-Spiel; or last paragraph of the article “Gothic Chess”, in issue 47 (2005) (p. 40). His posture contrasts with the one maintained by variant creators like Clément Begnis, the author of an interesting modernisation of Albers’ Courier-Spiel (no Alibabas here!). See link:
    http://clement.begnis.free.fr/

    Perhaps it’s only a personal taste issue, but I rather favor Byway’s arguments in this case.

    • Yes, I’ve also read of Byway’s take on Courier Chess! I do plan to add it to Ai Ai eventually, but I may take some time to get to it 🙂

      I’ve read Byway’s pieces in Variant Chess, and while I don’t begrudge him his perspective, I can’t say I agree with him. In particular his objections to Courier-Spiel seem rooted in aesthetics; he decries it as not being a ‘very elegant construct’, and says the ‘searchlight glare of powerful pieces washes out any subtle shades’. Of course he’s entitled to his opinion, but given the tactical spice and excitement I find in the higher-powered 12×8 variations, I don’t find it very convincing. As a player of large Shogi games I also am confident that strong pieces, in fact *very* strong pieces, are completely viable in Chess games and can add incredible tactical and strategic depth when used carefully.

      The argument in VC47 has some more substance to it. I agree that in some cases the use of slower pieces is a benefit; after all, I do enjoy the large Shogi games, which have hordes of slow single-step movers alongside the powerhouse pieces. But the removal of the Sage and Fool in favour of two Ferzes is unfortunate, in my opinion; this gives the game too many colourbound pieces, too little variety for the size of the board, and too many slow diagonal-movers. The whole array ends up feeling out of balance for me. Not that original Courier is perfectly balanced, far from it, but the Sage and Fool add some flavour. I also struggle with the additional first moves Byway grants to the Ferz and King; for agreement with modern conventions, I prefer only the Pawns having an initial double-step, plus these additional moves add more rules to remember.

      I like Reformed Courier-Spiel, and definitely want to add this to Ai Ai as well. The alterations to Albers’ game are logical, and avoid an overabundance of diagonal movers. On the whole I feel it’s a worthy successor to the venerable Courier game.

      In any case, I will eventually add both to Ai Ai and encourage everyone to try them both! Modern Courier Chess is a good game, it’s just not 100% to my taste. I’m keen to hear what players think, and I’d happily play a game of any of these variants when asked.

      Thanks for reading, and for sharing your point of view! I’m happy to see others are interested in the elongated forms of Chess as well 🙂

      • Hi again! Inspired by your comment, I have now coded both Reformed Courier-Spiel and Modern Courier Chess for Ai Ai 😀 They will be available in the next release.

        When I have time, probably this weekend, I will add entries for both games to this post, so that readers will know these great variants are available now.

        Thanks again for reading!

  2. Juan L. says:

    Fantastic! I have played Reformed Courier-Spiel with joclyboard (the last version of joclyboard doesn’t work anymore in my PC), but so far I never had the chance to play MCC agains an engine. I have installed openjdk 17 and Ai Ai 5.0.1.0. Waiting eagerly for the next version! Thank you very much!

  3. Juan L. says:

    Hi Eric! I have downloaded the last release of Ai Ai and tested Reformed Courier-Spiel (RCS) and Modern Courier Chess (MCC). RCS rules are easier to implement, I think (I managed to implement them on my installation of Fairy-Stockfish + XBoard), but MCC is another story, with all these optional initial moves for Ferzes and King. Your implementations seems absolutely perfect for RCS and… almost perfect for MCC. The optional initial double move for the King in MCC must consist on two legal moves away from the initial position in g1. That implies the King should never move through check. As Paul Byway said (Variant Chess, Issue 27):

    […] The usual double pawn move and en passant rules operate, but there is no castling: the king instead may make two king-moves in one turn (but not to capture), and as with castling he may not use this privilege to move out of or through check. For instance the Kg1 may go to h3, but there must be a clear, check-free path via g2 or h2.[…]

    For example, after the moves:
    1. f4 f5 2.e4 e5 3. fxe5 fxe4 4. g4 g5
    The White King can now make use of his double move privilege to play 5. Kh3, or 5. Kg3 (no problem to pass through g2), but not 5. Ke3 nor 5. Ke2, because of the Black Queen’s action on f2. The present Ai Ai implementation accepts correctly 5. Kh3 and 5. Kg3, but accepts incorrectly both 5. Ke3 and 5. Ke2.

    Despite this little detail, a very good job! Thanks!

    • Ah yes, you’re right — the move generator is not checking the intermediate squares for check. Unfortunately this means I have to completely rewrite the code for Modern Courier’s King, which is a bit annoying! I will work on fixing this for the next release, of course.

      Thanks for checking, and for your clear description of the issue!

  4. Juan L. says:

    Hi again! I’ve just found another issue in Ai Ai’s implementation of Modern Courier Chess. An unmoved Ferz should be able to do an optional Alibaba move, even when he is under attack. For example:
    1. e4 d6 2. Qb5 (attacks the Ferz in e8)
    and the moves 2…Fc6, 2… Fe6 or 2…Fg6 should be allowed, but they aren’t. After 2… Nd7 3. f4 the moves 3…F[cdg]6 are allowed again…

    • I had a strange moment when I read this comment, as I realised that I’d gone to some trouble to ensure that the Ferz could not do its Alibaba step when attacked, and now I’ve no idea why I did that! Strange.

      In any case, that problem is now fixed. I believe the King is now also working properly, but I had to repurpose the Chu Shogi Lion code for this so it will require more testing; multi-move pieces can cause all sorts of weird problems. Assuming it passes muster, then these fixes will appear in the next Ai Ai release.

      I wish MCC used the King’s Leap, like Jean-Louis Cazaux’s variants (and medieval Chess). The double-move thing is a pain, it needs more calculation and undoubtedly slows the AI down a tiny bit.

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