Capablanca's Chess is a well-known modern variation on Chess. It was devised by the famous Cuban world Chess champion José Raoul Capablanca sometime around 1921. Its array is:
R Kt Pr B Q K B Em Kt R
but the Princess is called an Archbishop, and the Empress is called a Chancellor. The board was originally 10 squares wide, but 8 squares deep, and it was noted that it can also be played on a 10 x 10 board, in which case the pawns can also move three spaces on their first move. But I've seen recent accounts of Capablanca's Chess that only mention the 10 x 10 version, despite the fact that after Capablanca played some games of this variant with Edward Lasker, they agreed that the version on the 8 x 10 board was superior.
The name used for the Empress in that game came from Chancellor Chess, invented in 1887 by Benjamin R. Foster. In that game, only the Empress is added. The array for that game is:
R N B Q K Em N B R
Since only one piece is added, the Knight and Bishop on the Chancellor-side are reversed so that Bishops will be on opposite colors.
A variation with the same complement of pieces as Capablanca's Chess was devised by H. E. Bird for the 8 x 10 board, but with the arrangement:
R Kt B Em Q K Pr B Kt R
In his version of the game, the Princess is called a Guard, and the Empress is called an Equerry. This version was first described on page 111 of Volume I of the City of London Chess Magazine, in what I take to be the June 1874 issue.
The book Chess Eccentricities credits Carrera with designing, in 1617, and again on an 8 x 10 board rather than on a 10 x 10 board, a version with the layout:
R Pr Kt B Q K B Kt Em R
with the Princess called a Centaur, and the Empress called a Campione. This early extended version of Chess is also mentioned in B. R. Foster's 1889 book about Chancellor Chess.
Personally, I strongly prefer Carrera's arrangement from among those that have been tried adding the Princess and Empress (for which I use A. S. M. Dickins' nomenclature) since the central part of the array remains the same, with the Bishop and Knight both covering the Q2 and K2 squares. The fact that the Princess and Empress both have the Knight move as one of their moves, of course, also means that a solid wall of Pawns in front of the position after Castling remains possible, even with the new pieces in the outer part of the array.
However, Capablanca's Chess has the advantage of having the powerful pieces, the Queen, the Rooks, and the Princess and Empress, evenly spaced. Incidentally, Capablanca's first version of his Chess variant was almost the same as that of H. E. Bird, except that the Princess was beside the Queen, and the Empress was beside the King.
Yet another variant of Chess with this same complement of pieces is noted as having been called Universal Chess, with all the pieces being renamed with military-themed names, by Dr. Bruno Violet in 1928; two arrangements of the board were provided, one of which was so similar to that of the earliest version of Capablanca's Chess, the one that closely resembled the game devised by H. E. Bird, that I thought it was the same.
However, that arrangement was different in a subtle way: the pieces on the back row were in this order:
R B Kt Pr Q K Em Kt B R
with the Bishops moved out to be beside the Rooks. This gives them improved access to the center of the board.
A photograph of a chess set for this game appears in A History of Chess by Jerzy Giźycki, but without the name of the inventor being given; this book is perhaps the first place where I heard of Gliński's hexagonal chess.
No listing of variants of Chess in which the additional pieces are the Princess (Knight+Bishop) and the Empress (Knight+Rook) would be complete, however, without taking note of what is perhaps the most recent major variant of this type: Seirawan Chess. Actually, that is the name the Chess world gave that variant by default when it was first introduced without a name, but now its creator has given it the official name of Sharper Chess.
Designed by noted grandmaster Yasser Seirawan, this variant is played on the normal 8 by 8 Chessboard, with the normal initial array of pieces.
I had mistakenly thought it was similar to one of the few variants of Chess that has often been played by real Chess players for entertainment, Pocket Knight Chess. In Pocket Knight Chess, each player has a third Knight which he can enter on the board at some point during the game instead of making a move. Surprisingly, at least to me, it is permitted for that Kight, as a result of its initial placement, to give check or even inflict checkmate.
This game is said to be particularly popular in the Netherlands, and it is also noted that a few tournaments of this variant have been played.
Unlike Chess, Go has not yet reached the point where computers are able to play the game better than almost everyone. One important reason for this is that an immense number of moves is possible at each step, since a stone can be played to any vacant location on the board.
This is an important advantage that is also shared to a lesser extent by Pocket Knight Chess, since until the pocket Knight is entered on the board, all the possible moves of entering it on the board also remain to be considered.
In Pocket Knight Chess, each player has a third Knight in addition to the two initially on the board. When it is a player's turn during the game, the player has the option of placing that Knight, if it has not already been placed on a previous move, on any vacant square on the board: there is no restriction preventing this move from giving check, giving mate, or responding to a check by interposition.
In Seirawan Chess, each player has both a Princess and an Empress off the board, the Princess being called a Hawk and the Empress being called an Elephant. But they aren't put on the board in the fashion that the Pocket Knight is, or a captured piece in Shogi.
Instead, when one of the pieces (other than a Pawn) makes its first move from its position in the initial array, as part of that move, the Hawk or the Elephant can be entered on the board.
It is not allowed to place both the Hawk and the Elephant on the board by means of Castling; at most one piece can be entered each move.
This is an ingenious way to approximate having the two new pieces as part of the initial array without having to enlarge the board. It does create enough additional variety in the initial layout to reduce the importance of memorizing opening variations as well.
This mechanism of entering additional pieces to a board that retains the conventional 8x8 size has been further refined in what looks to me to be a very interesting new variant of Chess, the game of Musketeer Chess.
This game was invented in 2011 by Dr. Zied Haddad.
The pieces are set up in the conventional initial array for normal Chess. Behind each player's pieces, there is a row of spaces which are not part of the normal playing board.
There are ten additional special pieces in each player's set of pieces, two of which will be used in any given game.
These ten pieces are:
Leopard: This piece may move as a Knight, or it may move one or two spaces as a Bishop.
Cannon: This piece may move one space in any direction (like a King, but without Royal powers), it may leap two spaces orthogonally (the move of a Dabbaba), or it may leap like a Knight, but only two squares horizontally and one square vertically.
Unicorn: This piece combines the moves of the Knight and the Camel; its leap is one square in one orthogonal direction, and either two or three squares in a perpendicular direction.
Dragon: This piece has the move of the Amazon, it combines the powers of the Queen and the Knight.
Chancellor: This piece has the move of the Empress, it combines the powers of the Rook and the Knight.
Archbishop: This piece has the move of the Princess, it combines the powers of the Bishop and the Knight.
Elephant: This piece may move one space in any direction (like a King, but without Royal powers), or it may leap two squares either orthogonally or diagonally. Thus, it combines the moves of the Man, the Alfil, and the Dabbaba.
Hawk: This piece may leap either two squares or three squares, and either orthogonally or diagonally.
Fortress: This piece may move like a Bishop, but only one, two, or three squares. It may also leap two squares orthogonally. As well, it may leap like a Knight, but only two squares vertically and one square orthogonally (the opposite of the restricted Knight move that the Cannon has).
Spider: This piece may move like a Bishop, but only one or two squares, it may leap like a Knight, or it may leap two squares orthogonally (the move of a Dabbaba).
White selects one of the two pieces to use, and then Black either selects the other piece to use, or rejects White's choice, in which case the game is played with a default pair from among the additional pieces, consisting of the Cannon and the Leopard.
Then the players take turns, starting with White, placing one of their two extra pieces in a particular space behind their men.
The significance of this is that the extra piece enters the game when the square in front of it is vacated.
It is not allowed, however, to place one piece behind the King, and the other behind a Rook, so that there is no chance of Castling causing two pieces to enter the game at once.
Note that Musketeer Chess includes a piece with the move of the Princess, called the Archbishop, and a piece with the move of the Empress, called the Chancellor; and it also includes a piece called the Hawk and a piece called the Elephant, but with different moves, these being the names used for the pieces with the moves of the Princess and the Empress in Seirawan Chess.
The pieces for Musketeer Chess are available commercially, but instead of being sold in one complete set, they are sold in sets which include both the White and Black pieces for two of the additional pieces; the sets are:
Fortress and Unicorn Dragon and Spider Elephant and Hawk Chancellor and Archbishop Leopard and Cannon
To play Seirawan Chess, therefore, one could choose either to buy just the Elephant and Hawk set, or just the Chancellor and Archbishop set, depending on whether one wishes to go by the names of the pieces, or by their moves in Musketeer Chess.
And, of course, the Chancellor and Archbishop would also serve for Capablanca Chess in both name and move. Thus, the set of pieces made for Musketeer Chess is also useful for people who want to play either Seirawan Chess or Capablanca Chess instead.
Yasser Seirawan's own site for Seirawan Chess/Sharper Chess refers people to the Elephant and Hawk set for Musketeer Chess on the House of Staunton web site, so apparently this is amicable, and not a plot to profit from the invention of Yasser Seirawan and Bruce Harper in a sneaky fashion. Which only makes sense; it is not as if there is much in the way of profits to be had from this sort of thing.
A further variant of this kind uses the Chancellor and Archbishop as pieces in hand, similarly to Sharper Chess, but in this version, they may be placed on the board on any vacant square in the back rank on any move, provided the player is not in check, and the move does not give check. This is Camaratta Chess, also called C-Chess. Incidentally, Frank Camaratta designed the chess pieces currently available for Musketeer Chess.
Also related to the variants in which the added pieces are the Princess and the Empress is Cagliostro's Chess, with the array:
R Kt B Pr Em Q K Am Pr B Kt R
In this game, the Princess is again called an Archbishop, the Empress is again called a Chancellor, and the Amazon is called a General. This game, played on a 12 by 8 board, includes quite a few powerful pieces.
It is named after its inventor, who lived in Florida, and invented it in or before the 1950s, not after the famous historical European reputed to dabble in sorcery.