Strategy--Checker play

 Containment positions

 From: Brian Sheppard Address: bsheppard@my-dejanews.com Date: 15 July 1998 Subject: Re: Lessons from the board -- #2 Forum: rec.games.backgammon Google: 6oic69\$g5l\$1@nnrp1.dejanews.com

```Michael J. Zehr wrote:
>            +24-23-22-21-20-19-------18-17-16-15-14-13-+
>            | O  O  O     O    |   |     X           X |
>            | O  O  O     O    |   |                 X |
>            | O     O     O    |   |                   | S
>            | O                |   |                   | n
>            | 6                | X |                   | o
>            |                  |BAR|                   | w
>            |                  |   |                   | i
>            |                  |   |                   | e
>            |       X          |   |                   |
>            |       X     X  X |   |     X  X          |
>            |       X  O  X  X |   |     X  X          |
>            +-1--2--3--4--5--6--------7--8--9-10-11-12-+
>            Pipcount  X: 133  O:  55  X-O: 0-1/5 (1)
>            CubeValue:  2, O owns Cube
> X to play (6 3)
>
> After bar/19, X has two choices for the 3: 19-16 or 17-14.  (13-10
> leaves a direct shot and should be discarded.)
>
> The normal guideline is to stay back as far as possible with 17-14.
> Here that is the wrong approach, however.  The more precise strategy is
> to try to aim for a spot 11 pips away from O's back checker.  The
> closest X can come to that is with 19-16.

Excellent analysis, Michael.

I have found two principles extremely helpful in containment positions.
Applying these principles will usually produce the correct moves.

The most important priority in a containment position is to hit the enemy
man. This priority works towards the goal of reducing the number of
opportunities the opponent has of rolling a 6-6 to win the game outright.
You may have a judgment call if the opponent cannot be hit safely, but the
principle of "when in doubt, hit" applies here; you should hit unless you
are certain that hitting is wrong.

If you cannot hit an enemy man, then your goal is to prevent escape. There
are two tactical goals in this strategy. You should make points close to
the enemy man, and keep blots far away (12 or more pips). Nearby points
directly impede the enemy's progress, but nearby blots do not. The opponent
is more likely to hit or skip over a nearby blot than he is to offer a
direct shot to it. Nearby blots should be moved into attacking position, so
that you can attack on subsequent turns if the opponent does not escape
this turn.

These principles cover the majority of containment situations. However,
there are plenty of times when priorities conflict. In those situations you
have to fall back on careful calculation of variations, as Michael pointed
out in his original post.

Warm regards,
Brian Sheppard

(BTW: the neural networks I am familiar with do not play according to these
principles unless they search at least 3 ply ahead. You can think of these
principles as encapsulating the understanding of a 3-ply lookahead.)
```

### Strategy--Checker play

Avoiding major oversights  (Chuck Bower+, Mar 2008)
Bearing off with contact  (Walter Trice, Dec 1999)
Bearing off with contact  (Daniel Murphy, Mar 1998)
Blitzing strategy  (Michael J. Zehr, July 1997)
Blitzing strategy  (Fredrik Dahl, July 1997)
Blitzing technique  (Albert Silver+, July 2003)
Breaking anchor  (abc, Mar 2004)
Breaking contact  (Alan Webb+, Oct 1999)
Coming under the gun  (Kit Woolsey, July 1996)
Common errors  (David Levy, Oct 2009)
Containment positions  (Brian Sheppard, July 1998)
Coup Classique  (Paul Epstein+, Dec 2006)
Cube ownership considerations  (Kit Woolsey, Apr 1996)
Cube-influenced checker play  (Rew Francis+, Apr 2003)
Defending against a blitz  (Michael J. Zehr, Jan 1995)
Estimating in volatile situations  (Kit Woolsey, Mar 1997)
Gammonish positions  (Michael Manolios, Nov 1999)
Golden point  (Henry Logan+, Nov 2002)
Hitting loose in your home board  (Douglas Zare, June 2000)
Holding games  (Casual_Observer, Jan 1999)
How to trap an anchor  (Timothy Chow+, Apr 2010)
Jacoby rule consideration  (Ron Karr, Nov 1996)
Kamikaze plays  (christian munk-christensen+, Nov 2010)
Kleinman Count for bringing checkers home  (Øystein Johansen, Feb 2001)
Late loose hits  (Douglas Zare+, Aug 2007)
Mutual holding game  (Ron Karr, Dec 1996)
Pay now or pay later?  (Stuart Katz, MD, Nov 1997)
Pay now or pay later?  (Stephen Turner, Mar 1997)
Pay now or play later?  (Hank Youngerman+, Sept 1998)
Play versus a novice  (Courtney S Foster+, Apr 2004)
Playing doublets  (Grunty, Jan 2008)
Playing when opponent has one man back  (Kit Woolsey, May 1995)
Prime versus prime  (Albert Silver+, Aug 2006)
Prime versus prime  (Michael J. Zehr, Mar 1996)
Saving gammon  (Bill Riles, Oct 2009)
Saving gammon  (Ron Karr, Dec 1997)
Splitting your back men  (KL Gerber+, Nov 2002)
Splitting your back men  (David Montgomery, June 1995)
Trap play problem  (Brian Sheppard, Feb 1997)
When in doubt  (Stick+, Apr 2011)
When to run the last checker  (Stick Rice+, Jan 2009)
When you can't decide  (John O'Hagan, Oct 2009)