Opening moves in backgammon – Part III

We are going to be analyzing three more opening rolls in this, Part III of our series of articles looking at opening moves.

In this article we are going to look at the following rolls: 21, 41, 51
Each of these rolls can be played in at least two ways and as usual we are going to show you the pro’s and con’s of each way of playing them.

If we were in the 70’s this article would be short indeed,at that time everyone played the one (1) 6/5. The common assumption at the time was that splitting the rear checkers (ie playing 24/23) was not done. At the time slotting key points and estabishing them on the next roll was the way to go.

Years have passed since then and with the coming of computers we can now establish that there are arguments for both options.
Slotting the 5 point by playing 6/5 is an attempt to establish your own 5 point as early as possible. If your opponent doesn’t hit the blot then you will be a strong favourite to establish the point on your next turn. The game may then evolve into many different types but quite often it will become a prime vs. prime game, this being the most difficult of all backgammon games to play.

Be aware then that slotting will often lead to complex positions on the board. Splitting, on the other hand, often evolves into much simpler positions, most typically mutual holding games or high anchor positions.

This brings us to the issue of analysing your strength against that of your opponent and how to adjust your play based on that analysis. If you are the stronger player you should opt for complex and long games and you should attempt to slot. The more complex the position the more chance there will be for your weaker opponent to make mistakes– the longer the game the more chance you will have to bring into play your superior experties.

Obviously if you are the less experienced player you should aim to avoid complexity and you should go for simple positions. This would lead to splitting rather than slotting.

Please note that in tournament matches the leader should strive for simple games and the player behind should aim for complex games (slot). This is because the slot will lead to many more gammons than splitting and the player behind in a match should be aiming for gammons.
The actual rolls (split or slot)


In this case let us ignore the beginner’s move 13/10. The opening is the time when we can take risks to strengthen our position and whilst 13/10 unstacks a heavy point and prepares to make new points it is not as dynamic as the other two moves, both of which accomplish 2 good things.

The first move we look at is 13/11, 6/5, as shown below;


This will unstack the two heaviest points and slots the most important point on the backgammon board- your own 5-point . If red does not hit this blot (and he is not favorite to do so) then black is an overwhelming favorite to establish the point on his next turn.

If red does hit the blot then the black blot on the 11 point is well placed to return hit on the 5 point next turn. This is because it is six points away from the blot and a 6 is the one number black is unable to use to re-enter the board.

The other option is to play the split, 13/11, 24/23:


The aim of the split is two fold. It makes it more dangerous for red to move builders into his outer board and it gives black several good rolls next turn to establish an advanced anchor, e.g. 32 played 24/21, 23/21.

The split involves less risk than the slot and subsequently the rewards are not as high. If you pull of the slot you will own your 5 point , a major improvement. When the split shows a profit it is usually in the way of an advance anchor or a hit in reds outer board. These are gains that cannot be ignored but establishing the 5 point is the biggest gain you can make in the beginning of a game of backgammon.
41 Can we just apply the same arguments to 41 and come up with the same answers?

The answer to this is no, and we must take a much deeper look.

Again we shall ignore the beginner’s move 13/8 for much the same reasons we discarded 13/10 as an alternative move for our 21 opening. Whilst it is completely safe and does bring another useful builder to black’s 8 point, it just doesn’t do enough at a time when you should be taking risks to improve your in game position.

Let us look at the viable moves

First the slot, 13/9, 6/5:


and second the split, 13/9, 24/23:


The theory of slot vs. split will apply to these moves just as they did to our 21 opener. However, there are a number of mathematical differences that make this a much closer call than before

  • After playing the slot, red has 19 hitting numbers (as opposed to 15 after 21) because he now hits with 62 and 53 as well as with all 4’s.
  • Because black’s builder is on the 9-pt rather than the 11-pt he has more point making rolls next turn even without slotting so it is possible that slotting may be too much of a good thing
  • If the slotted blot is hit then black will no longer have a builder placed the optimal 6 points away and the checker on the 9-pt is much less effectively placed for hitting back.

These may appear to be very small differences but small differences is what backgammon is all about and the computer software today, would lead us to believe that these differences are big enough to make the split 13/9, 24/23 the correct play with an opening 41.

I feel they are most likely correct but that does not take into account the opponent factor. Against a weaker player I will always play 13/9, 6/5 seeking the complex game that I believe will give me the edge. Against an opponent of equal strength or a stronger opponent I will play for 13/9, 24/23.

One final note on 41. There are some other alternatives such as 24/20, 24/23 and 24/20, 6/5. Over time these moves have been discounted from the list of serious contenders. The first because it does not take the option of unstacking the overloaded mid point and the latter because it is just too boldto play , as we shall see subsequently, splitting and slotting in the same move is almost never correct.


This brings us to 51. Again there are some subtle differences. Let’s analyse the two moves, starting with slot, 13/8, 6/5:


and now the split, 13/8, 24/23:


The problem with both of these moves is that the ‘5’ does not really improve black’s game position. Black already has a spare builder on his 8 point. Another checker there is only a slim improvement at the very best. However, most 5’s play poorly in the opening and we have to play what the gods of dice give us. 13/8 is really the only option available to us here.

The issue with the slot is that if red misses the shot at the blot, whilst still favorite to make the 5-pt, black only has a 2-1 chance to do so rather than being the big favorite after the 21 and 41 slot plays.

For this very reason the computers once again prefer the split play 13/8, 24/23, although it is a very close call. As in the notes to the 41 play I always play the slot against weaker opponents and in this instance also against equal opponents. Only against a much stronger opponent will I play the split option.

With 51 there is a also a 3rd alternative that did gain some popularity a few years ago but I have not seen this played very often lately. I think, however, that it is worth taking a look at. The move is 24/18, as show below:


The logic behind this play is very similar to that for the 62 and 63 moves that we have already taken a look at . It aims to enable black to either make red’s bar-point next turn or to promote an advantageous (to black) sequence of hits on red’s bar point. It also uses the 5 effectively which neither the slotting nor the splitting play do.


So there it is. With 21 it is seems fairly obvious that the technically best move is 13/11, 6/5 but do not forget to consider your opponent and match score.

Just as obvious with 41 the correct play is 13/9, 24/23 because slotting in this situation can be viewed as overkill.

With 51 the verdict is undecided and the slot and the split are very close with the computers tipping the balance in favor of playing the split.