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Modern Chess was invented by Gabriel Maura in 1968. In 1972 a controlling body (FENDAM) was formed with delegates representing 16 countries. The first Modern Chess World Championship was held in Puerto Rico 1974. The World Correspondence Championship of Modern Chess was held in the years 1976-1983. Organized events seized in 1983.

Although a fully playable variant, it is curious why 'Modern Chess' attracted that much attention. If the Prime Ministers (Cardinals) are exchanged, what remains is a slow and drawish version of orthochess. The pawns cannot meet immediately in the middle of the board. The fact that the bishops move on the same colour depletes the strategical content, I suppose.
/Mats

The real purpose of this post is as follows: The Eight Officers Problem is impossible. Since the goal of Modern Chess was to increase mobility, that suggests that the 'Nine Officers Problem' should have a solution.

The Eight Officers Problem, for traditional chess, is the following: Is it possible to take a king, a queen, 2 bishops, 2 knights, and 2 rooks, and place them on a blank 8x8 board (with bishops on opposite colored squares) so that every square is attacked? (A piece does not attack the square it occupies.)

The Nine Officers Problem would be: Is it possible to take a king, a queen, a Prime Minister, 2 bishops, 2 knights, and 2 rooks, and place them on a blank 9x9 board (with bishops on Same-colored squares) so that every square is attacked?

Just created a new preset for Modern Chess:
/play/pbm/play.php?game%3DModern+Chess%26settings%3DModern+Chess

I just discovered this variation in Puerto Rico while on vacation there when I played chess with some friends at a park in Manati.

Sissa is a 9x9 chess variant invented in 1998 by Carlos Cetina, using his Bishops Conversion Rule. I do not recall anyone else including his rule in a chess variant. In Caïssa Britannia (Fergus Duniho) the Bishop may also step one space orthogonally without capturing - any Bishop, any number of times.

>> Is there any provision in Modern Chess allowing the Bishops to 
>> Change to opposite Diagonals?

Yes there is.

There is a 'Bishop-Castling' or 'Bishop Adjustment' rule.

For only ONE of the bishops, you can 'castle' (switch positions) with either the Knight, Queen or Minister next to it, therefore moving that Bishop to the white squares.

The Bishop in question must have not moved before 'castling', and the Knight, Queen or Minister to 'castle' with must have not moved either.

I'm trying to get a copy of the original book from Gabriel Maura from a friend in Puerto Rico, to formalize the rules, and request an update to the rules page in Chess Variants.

Haven't heard of the Bishop's one square ortogonal move in Modern Chess, but will ask for the clarification.

Excellent Antoine! Thanks!

Does it enforce that only one Bishop can castle per side?

Thanks Antoine.

= = =

I just received today in the mail an original Spanish copy of Gabriel Vicente Maura's 1973 3rd edition 'Mathematical Thesis for Modern Chess including the Prime Minister'!!!

I found it in a Library of Antique Books in Madrid, Spain.

Nice little book (it's only 48 pages long).

It has Gabriel Vicente Maura's 'mathematical' explanation of why the chess board needed to be increased in size to 9x9, why a new powerful piece needed to be added to the game, and why that piece needed to be a Prime Minister (Bishop + Knight).

Interesting 'mathematical' theory.

I'll digest it first, and post a summary of his theory.

BTW. The book confirms the Bishop Castling rule as I've described before. 

The rule is actually called the 'Bishop Adjustment' rule.

In the true nature of Modern Chess, Maura believed the game was better to be played with both Bishops on the dark squares.

But he left the possibility open for players that couldn't let go (of having Bishops in opposite colors).

I'm working on the code for two new presets for Chess Courier for randomized variants for Modern Chess:

Modern Random Chess and Modern Fischer Random Chess

I'm trying to reuse some of the code already done for Fischer Random Chess, and found a statement that is too specific in the fischer.txt include file, that prevents this include file to be general enough to be used for 9x9 variants.

In the subroutine to evaluate actual moves by the Black Rook, in the elseif statement there is a reference to a physical coordinate (f8), rather than to a label (#roo):

sub r from to;
  set legal fn R #from #to;
  if not var legal or == old k:
    if == #to #rooo:
      castle #k #kooo #from #rooo;
      set k #kooo;
    elseif == #to f8:
      castle #k #koo #from #roo;
      set k #koo;
    endif;
  endif;
  unsetflag #from;
endsub;

The same is not the case for the subroutine for evaluating actual moves by the White Rook:

sub R from to;
  set legal fn R #from #to;
  if not var legal or == old K:
    if == #to #ROOO:
      castle #K #KOOO #from #ROOO;
      set K #KOOO;
    elseif == #to #ROO:
      castle #K #KOO #from #ROO;
      set K #KOO;
    endif;
  endif;
  unsetflag #from;
endsub;

Here the elseif has a #ROO label that allows this subroutine to be general enough to work for a 9x9 chess variant.

Can someone update the subroutine for black in fischer.txt to have the label #roo instead of f8?

Second question, how do I upload a new file into the include library?

I'm working on the code for a new modern-adjustment.txt file that will be general enough to provide for my new Bishop Adjustment in the randomized versions I'm working on, as well as for the Bishop Commuting found in the modern.txt include file.

Thanks.

Thanks for discovering the bug. I've replaced f8 by #roo.
I don't think there is presently a way for users to upload include files. I guess you can write your functions in the pregame field of your presets for debugging sake and send me include files when you're satisfied with them.

Thanks Antoine!

Can you update the Modern Chess webpage to include the 'Bishop's Adjustment' rule?

http://www.chessvariants.org/large.dir/modern.html

Below is my English interpretation of the rule, which appears in Spanish on page 32 of Gabriel Maura's 1973 'Tesis Matematica del Ajedrez Moderno' (Mathematical Thesis for Modern Chess):

==

The Bishop Adjustment Rule

It consists in exchanging the square of one of the Bishops with either of the adjacent major pieces - the Queen or the Queen's Knight on the right, or the Minister or Minister's Knight to the left - as long as neither of the pieces being exchanged has been moved from its original square.

The player would have four ways to do the adjustment, but he is only allowed to do it one time throughout the game, if he wishes to. This adjustment counts as a move, just like castling. The notation for it is: B=MN (example for the adjustment with the Minister's Knight).

Thanks for updating the Modern Chess page with the Bishop Adjustment rule.

I found two typos.

1. The notation for the Bishop and Minister's Knight example is actually
B=MN (I made a mistake before with B=MK).

2. The international organization created that arranged tournaments and
world championships for Modern Chess was FEMDAM. (not FENDAM as Pritchard
incorrently quotes in his book).

FEMDAM = FEderacion Mundial De Ajedrez Moderno

which is Spanish for 'World Federation of Modern Chess'

Can someone please update the two typos in the Modern Chess page? 

http://www.chessvariants.org/large.dir/modern.html

[All fixed, I think. DH] [Yes. Thanks. JC]

Can one of the admins for the site update the links at 

http://www.chessvariants.org/index/mainquery.php?type=Any&startswithletter=M&orderby=LinkText&displayauthor=1&displayinventor=1

to include a link to the Modern Chess preset for Game Courier?

The Modern Chess preset's link is:
/play/pbm/play.php?game%3DModern+Chess%26settings%3DAlfaerie

The 'See Also' page for Modern Chess:

http://www.chessvariants.org/index/displayitem.php?itemid=Modernchess

needs also to be updated with the link to the Chess Courier preset above.

Thanks in advance.