# Retroanalysis and Checkers

Gert Wilts, 19 Mar 1995

```In the book "Histoires extraordinaires" from Jean Bertin, France,
there is an example of RA in the game of draught (checkers).
Unfortunately I don't have the book at hand so that I cannot copy
this example.```

### Gerd Wilts, 7 Apr 1995

```The following is an example of RA in the game of checkers, taken from the
book "Histoires extraordinaires sur 64 cases" from Jean Bertin, France.```
```+----------+
+          +
+          +
+    b b   +
+     B    + <--- How could this pawn have reached its square?
+    b b   +
+          +
+  B       +
+          +
+          +
+   B B    +
+----------+
Black to move. ```
```I don't know the rules of checkers. Can anybody tell me if this is
an interesting example of RA?```

### Joseph Kisenwether, 10 Apr 1995

`The position posted for the retro's checkers problem by Jean Bertin was:`
```White: c4,d1,f1,f7; Black:e6,e8,g6,g8  (On a 10x10 board)
Black to move, explain how the checker on f7 got there.```
```I fiddled with this for a while (at first I didn't realize that the board was
supposed to be 10x10 having missed the previous post in which a diagram was
presented)```
```There are many different sets of rules for checkers, so the first problem is
figuring out exactly which game we are talking about here.```
```Unfortunately, all of the versions I know of that are played on a 10x10 board
are also played entirely on the dark squares of the checker-board, but all the
peices in position given are on the light squares.```
`By what rules are we playing?`
```(If you don't know could you please Email me the solution, Gerd, if the book
includes it?)```

### Joost de Heer, 10 Apr 1995

```I haven't found the solution to the problem yet. I assume the American rules
for checkers are used (no capture backwards, marjority capture isn't obligatory
and promoted piece (king? I don't know the term in English) moves only 1
square also. The board is at least 8*8 (It came out of a book with '64' in the
title.```
```If capturing backwards is allowed, the problem is easy :
W e6,d5,a2,d1,f1
B e8,g8,g6,c4,b3      e6-f7 c4*f6 a2*c2```

### Gerd Wilts, 12 Apr 1995

`I would like to clarify some things:`
```Indeed the board used for this retro is a 10x10 board, and the position
is:```
```White: c4,d1,f1,f7; Black:e6,e8,g6,g8  (On a 10x10 board)
Black to move, explain how the checker on f7 got there.```
```The book doesn't give the author of this problem, but the author seems not
to be Jean Bertin. I don't know what set of rules is used for this problem.
The french text just states that it is the "jeu de Dames"; I assume that
this must be the game of draughts. The book gives the following solution:```
`Intermediate position:`
`White: e1, f6, g1, g5, i1; Black: d6, d8, f8, i3, i5.`
```Then:
1. 50-45, (30-34);
2. 23-18, (34x23); (le moins mauvais)
3. 45x34 gagne"```

### Joseph Kisenwether, 17 Apr 1995

```Ah... The problem that I had encountered with the problem is that the position
given has been mirror-imaged. The one posted was:```
`White: c4, d1, f1, f7   Black:e6, e8, g6, g8`
`What that should be is:`
`White: e1, e7, g1, h4   Black:  d6, d8, f6, f8`
```The game being considered is "International Checkers" in which unpromoted pieces
must move forward and digonally one square when not capturing and jump enemy peices
diagonally either forward or backward when capturing. You are obliged to make a
capture if you can and to continue jumping with that piece until it cannot do so
(i.e. if you make a jump to a square where the piece you are moving can make another
jump, it is mandatory to do so.)```
```Queens (or Dames) move like chess bishops and capture by making a bishop move over
the square on which the enemy man is standing (continuing any number of spaces
beyond) The enforced capture rule applies to them as well.```
```With that finally cleared up, the soluion posted, translated into algebraic notation
for those who do not play checkers is:```
`Intermediate position: `
`White: e1, f6, g1, g5, i1;   Black:  d6, d8, f8, i3, i5`
```1: i1-j2      i5-h4
2: f6-e7      h4xf6
3: j2xh4```
```Gerd had asked if this was a good example of retro-analysis. Actually, once you are
clear about what game you are dealing with it's very simple. As I mentioned in a
previous post to this list, I orignally began looking at this problem on the 8x8
board and invite you all to do this same. consider the analogous problem in
"Anglo-American Checkers":```
`White: c1, c7, e1, f4;    Black:  b6, b8, d6, d8`
```Anglo-American Checkers is played on an 8x8 board, men move as in International
Checkers, but may only capture forward. Kings (promoted men) move just as the
unpromoted men do, but can both move and capture forawrds and backwards. (There is
no need for king to enter into your solution though)
Anyway, How did the about position come to pass?```
```Now a technical question: If I use the 8x8 Anglo-Checkers problem above, who do I
list as the author, seeing as I actidentally discovered the problem while working
on a corrupted version of the problem from Bertins book?```