XGID=abbBCBDBB----------bbbbb--:1:-1:1:23:0:0:0:0:10

X:Player 1 O:Player 2
Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| | | O O O O O | +---+
| | | O O O O O | | 2 |
| | | | +---+
| | | |
| | | |
| |BAR| |
| | O | |
| | | X |
| | | X X |
| X X | | X X X X O O |
| X X | | X X X X O O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 82 O: 159 X-O: 0-0
Cube: 2, O own cube
X to play 23

---
Tim Chow

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

XGID=abbBCBDBB----------bbbbb--:1:-1:1:23:0:0:0:0:10

X:Player 1 O:Player 2
Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| | | O O O O O | +---+
| | | O O O O O | | 2 |
| | | | +---+
| | | |
| | | |
| |BAR| |
| | O | |
| | | X |
| | | X X |
| X X | | X X X X O O |
| X X | | X X X X O O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 82 O: 159 X-O: 0-0
Cube: 2, O own cube
X to play 23

The chapter on "Backgame Bear-In" in Trice's "Backgammon Boot Camp"
has a remark that has long been a source of confusion for me. Trice
writes, "Against a single anchor, it is usually right to 'clear from
the rear and don't ask questions,' as Kit Woolsey puts in. In
backgames there is a common exception: Clear the tough points when
you can." He then goes on to argue for clearing the next-to-the-last
point because it is opposed by two anchors, so that if you leave a
shot there then your opponent will have a double shot, whereas the
rearmost point is opposed by only one anchor.

The confusing point is that this principle applies more often to
13-backgames and 23-backgames than to 12-backgames. In the
aforementioned chapter, Trice discusses 4 positions, 3 of which
are 12-backgames, and one of which is a 23-backgame. It's the
23-backgame position where Snowie clears the next-to-the-last point.
Against a 12-backgame, clearing from the rear kills your large
numbers, whereas against a 13-backgame (respectively, a 23-backgame)
you have to worry about being forced to play a checker awkwardly to
your 2pt (respectively, your 1pt).

The position above may look like a contrived reference position but it
actually arose OTB for me. I played 7/5 7/4, but see the rollout below
and the two variants.

1. Rollout¹ 8/6 8/5 eq:+0.843
Player: 74.22% (G:40.70% B:6.80%)
Opponent: 25.78% (G:0.51% B:0.02%)
Confidence: ±0.010 (+0.833..+0.853) - [100.0%]

2. Rollout¹ 8/5 6/4 eq:+0.809 (-0.034)
Player: 73.57% (G:39.47% B:6.66%)
Opponent: 26.43% (G:1.13% B:0.04%)
Confidence: ±0.010 (+0.798..+0.819) - [0.0%]

3. Rollout¹ 6/4 6/3 eq:+0.786 (-0.056)
Player: 73.18% (G:38.86% B:6.10%)
Opponent: 26.82% (G:0.94% B:0.04%)
Confidence: ±0.011 (+0.776..+0.797) - [0.0%]

4. Rollout¹ 8/3 eq:+0.784 (-0.058)
Player: 72.96% (G:38.69% B:6.38%)
Opponent: 27.04% (G:1.09% B:0.04%)
Confidence: ±0.011 (+0.774..+0.795) - [0.0%]

5. Rollout¹ 7/5 7/4 eq:+0.735 (-0.108)
Player: 70.17% (G:39.67% B:7.73%)
Opponent: 29.83% (G:0.47% B:0.01%)
Confidence: ±0.013 (+0.722..+0.748) - [0.0%]

¹ 1296 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 3-ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.19.207.pre-release

---------
Variant 1
---------

XGID=abBbCBDBB----------bbbbb--:1:-1:1:23:0:0:0:0:10

X:Player 1 O:Player 2
Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| | | O O O O O | +---+
| | | O O O O O | | 2 |
| | | | +---+
| | | |
| | | |
| |BAR| |
| | O | |
| | | X |
| | | X X |
| X X | | X X X O X O |
| X X | | X X X O X O |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 80 O: 157 X-O: 0-0
Cube: 2, O own cube
X to play 23

1. Rollout¹ 7/5 7/4 eq:+0.469
Player: 62.42% (G:33.94% B:5.36%)
Opponent: 37.58% (G:0.55% B:0.02%)
Confidence: ±0.010 (+0.458..+0.479) - [100.0%]

2. Rollout¹ 8/6 8/5 eq:+0.413 (-0.056)
Player: 61.23% (G:32.20% B:4.62%)
Opponent: 38.77% (G:1.32% B:0.04%)
Confidence: ±0.009 (+0.403..+0.422) - [0.0%]

¹ 1296 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 3-ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.19.207.pre-release

---------
Variant 2
---------

XGID=aBbbCBDBB----------bbbbb--:1:-1:1:23:0:0:0:0:10

X:Player 1 O:Player 2
Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| | | O O O O O | +---+
| | | O O O O O | | 2 |
| | | | +---+
| | | |
| | | |
| |BAR| |
| | O | |
| | | X |
| | | X X |
| X X | | X X X O O X |
| X X | | X X X O O X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 78 O: 155 X-O: 0-0
Cube: 2, O own cube
X to play 23

1. Rollout¹ 7/5 7/4 eq:+0.377
Player: 60.57% (G:33.55% B:1.90%)
Opponent: 39.43% (G:2.39% B:0.08%)
Confidence: ±0.010 (+0.367..+0.387) - [100.0%]

2. Rollout¹ 8/6 8/5 eq:+0.309 (-0.068)
Player: 58.21% (G:32.58% B:1.66%)
Opponent: 41.79% (G:2.57% B:0.09%)
Confidence: ±0.011 (+0.298..+0.320) - [0.0%]

¹ 1296 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 3-ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.19.207.pre-release

---
Tim Chow

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

XGID=-ABbBBBBBB----------bcccb-:1:-1:1:21:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| | | O O O O O | +---+
| | | O O O O O | | 2 |
| | | O O O | +---+
| | | |
| | | |
| |BAR| |
| | | |
| | | |
| | | |
| X X X | | X X X O X |
| X X X | | X X X O X X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 83 O: 83 X-O: 0-0
Cube: 2, O own cube
X to play 21

---
Tim Chow

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Monday, April 24, 2023 at 8:29:05 AM UTC-4, Timothy Chow wrote:

XGID=-ABbBBBBBB----------bcccb-:1:-1:1:21:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| | | O O O O O | +---+
| | | O O O O O | | 2 |
| | | O O O | +---+
| | | |
| | | |
| |BAR| |
| | | |
| | | |
| | | |
| X X X | | X X X O X |
| X X X | | X X X O X X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 83 O: 83 X-O: 0-0
Cube: 2, O own cube
X to play 21

---
Tim Chow

Not sure, but I think you would want to have more than one point open in O's board before considering opening up a more proximal point, e.g. 7/6 7/5, so that if you're hit on the ace point or 3 point while carrying out your plan, you can get back in.
Bob

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

XGID=-ABbBBBBBB----------bcccb-:1:-1:1:21:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| | | O O O O O | +---+
| | | O O O O O | | 2 |
| | | O O O | +---+
| | | |
| | | |
| |BAR| |
| | | |
| | | |
| | | |
| X X X | | X X X O X |
| X X X | | X X X O X X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 83 O: 83 X-O: 0-0
Cube: 2, O own cube
X to play 21

Against an ace-point anchor, one typically clears from the rear. I've
cited Kit Woolsey's article before but I will cite it again.

https://bkgm.com/articles/Woolsey/AcePoint-DoYouKnowYourAcePoint/

Against a deuce-point anchor, clearing the bar point tends to be the
right idea, because you don't want to be forced to play 7/1 with your
sixed.

What about the three-point anchor? In a position like this one, we
would ideally like to set a trap and force O to run off her anchor.
Clearing the 7pt is not as effective because O can play a 4 in her
home board (for comparison, see the variant below). Clearing the 9pt
doesn't give us as many builders to pounce on the remaining checker
if O is forced to run with one checker.

1. Rollout¹ 8/7 8/6 eq:+0.598
Player: 80.52% (G:5.94% B:0.09%)
Opponent: 19.48% (G:0.62% B:0.01%)
Confidence: ±0.004 (+0.594..+0.602) - [100.0%]

2. Rollout¹ 7/6 7/5 eq:+0.509 (-0.088)
Player: 77.21% (G:5.18% B:0.07%)
Opponent: 22.79% (G:0.82% B:0.01%)
Confidence: ±0.004 (+0.505..+0.514) - [0.0%]

3. Rollout¹ 9/8 9/7 eq:+0.502 (-0.095)
Player: 77.32% (G:3.83% B:0.05%)
Opponent: 22.68% (G:0.87% B:0.01%)
Confidence: ±0.004 (+0.498..+0.507) - [0.0%]

¹ 1296 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 3-ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.19.211.pre-release

-------
Variant
-------

XGID=-ABbBBBBBB-----------dccc-:1:-1:1:21:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| | | O O O O | +---+
| | | O O O O | | 2 |
| | | O O O O | +---+
| | | O |
| | | |
| |BAR| |
| | | |
| | | |
| | | |
| X X X | | X X X O X |
| X X X | | X X X O X X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 83 O: 78 X-O: 0-0
Cube: 2, O own cube
X to play 21

1. Rollout¹ 8/7 8/6 eq:+0.626
Player: 81.34% (G:7.07% B:0.11%)
Opponent: 18.66% (G:0.57% B:0.01%)
Confidence: ±0.004 (+0.623..+0.630) - [54.4%]

2. Rollout¹ 7/6 7/5 eq:+0.626
Player: 80.20% (G:9.70% B:0.22%)
Opponent: 19.80% (G:0.67% B:0.01%)
Confidence: ±0.004 (+0.622..+0.630) - [45.6%]

¹ 1296 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 4-ply, cube decisions: XG Roller+
Search interval: Large

eXtreme Gammon Version: 2.19.211.pre-release

---
Tim Chow

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Wednesday, April 26, 2023 at 11:37:03 PM UTC-4, Timothy Chow wrote:

XGID=-ABbBBBBBB----------bcccb-:1:-1:1:21:0:0:0:0:10

Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| | | O O O O O | +---+
| | | O O O O O | | 2 |
| | | O O O | +---+
| | | |
| | | |
| |BAR| |
| | | |
| | | |
| | | |
| X X X | | X X X O X |
| X X X | | X X X O X X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 83 O: 83 X-O: 0-0
Cube: 2, O own cube
X to play 21
Against an ace-point anchor, one typically clears from the rear. I've
cited Kit Woolsey's article before but I will cite it again.

https://bkgm.com/articles/Woolsey/AcePoint-DoYouKnowYourAcePoint/

Against a deuce-point anchor, clearing the bar point tends to be the
right idea, because you don't want to be forced to play 7/1 with your
sixed.

What about the three-point anchor? In a position like this one, we
would ideally like to set a trap and force O to run off her anchor.
Clearing the 7pt is not as effective because O can play a 4 in her
home board (for comparison, see the variant below). Clearing the 9pt
doesn't give us as many builders to pounce on the remaining checker
if O is forced to run with one checker.

1. Rollout¹ 8/7 8/6 eq:+0.598
Player: 80.52% (G:5.94% B:0.09%)
Opponent: 19.48% (G:0.62% B:0.01%)
Confidence: ±0.004 (+0.594..+0.602) - [100.0%]

2. Rollout¹ 7/6 7/5 eq:+0.509 (-0.088)
Player: 77.21% (G:5.18% B:0.07%)
Opponent: 22.79% (G:0.82% B:0.01%)
Confidence: ±0.004 (+0.505..+0.514) - [0.0%]

3. Rollout¹ 9/8 9/7 eq:+0.502 (-0.095)
Player: 77.32% (G:3.83% B:0.05%)
Opponent: 22.68% (G:0.87% B:0.01%)
Confidence: ±0.004 (+0.498..+0.507) - [0.0%]

¹ 1296 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 3-ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.19.211.pre-release

-------
Variant
-------

XGID=-ABbBBBBBB-----------dccc-:1:-1:1:21:0:0:0:0:10
Score is X:0 O:0. Unlimited Game
+13-14-15-16-17-18------19-20-21-22-23-24-+
| | | O O O O | +---+
| | | O O O O | | 2 |
| | | O O O O | +---+
| | | O |
| | | |
| |BAR| |
| | | |
| | | |
| | | |
| X X X | | X X X O X |
| X X X | | X X X O X X |
+12-11-10--9--8--7-------6--5--4--3--2--1-+
Pip count X: 83 O: 78 X-O: 0-0
Cube: 2, O own cube
X to play 21
1. Rollout¹ 8/7 8/6 eq:+0.626
Player: 81.34% (G:7.07% B:0.11%)
Opponent: 18.66% (G:0.57% B:0.01%)
Confidence: ±0.004 (+0.623..+0.630) - [54.4%]

2. Rollout¹ 7/6 7/5 eq:+0.626
Player: 80.20% (G:9.70% B:0.22%)
Opponent: 19.80% (G:0.67% B:0.01%)
Confidence: ±0.004 (+0.622..+0.630) - [45.6%]

¹ 1296 Games rolled with Variance Reduction.
Dice Seed: 271828
Moves: 4-ply, cube decisions: XG Roller+
Search interval: Large

eXtreme Gammon Version: 2.19.211.pre-release

---
Tim Chow

Don't overlook the fact that when you clear from the rear in these situations there is no number for your opponent to leave both blots within' your grasp. If you clear an intermediate point, there will still be numbers that break anchor but don't run
all the way past your contact. With the best play here for example the opponent still has the nightmare [51].

Stick

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)