St John wrote:tahitiwahini wrote:So the best thing for the defender is to put 2 in each country, the next best thing is to put 1 in front and 3 in the rear, and the worst thing is for the defender to put 3 up front and 1 in the rear.
I get that 2 by 2 deployment is the better. But why is it better to deploy 1 in North AFrica and 3 in Brazil than vice versa? The Egyptian attacker has to overcome 1 army and 3 armies in two consecutive battles, what difference does it make in which order they are fought?
And by placing 3 in North Africa you also make it harder for the opponent to gain any land at all, so why place only 1 there?
Good question.
It's all about the dice.
We understand why 2,2 is a better defense so I won't go into that again.
Why is 1,3 (front,rear) a better defense than 3,1?
There are several important thresholds when attacking. For attackers these thresholds are:
>3 armies: attack with 3 dice
3 armies: attack with 2 dice
2 armies: attack with 1 die
1 army: can't attack anymore
For the defender they are:
>1 army: defend with 2 dice
1 army: defend with 1 die
Let's see what happens in a 6 army attack against a 1,3 defense:
The first attack is a 6 v 1.
These are the worst possible odds for the defender. Since it's the first attack the attacker is at the zenith of his strength (he will never be stronger). In our scenario you will have to endure one of these 3 v 1 dice attacks at some point. Why do you want to take it up front when the attacker is at his strongest? Because essentially the attacker's strength at this point is really overkill. In other words, the attacker's odds in a 6 v 1 attack are the same as his odds in a 5 v 1, which are the same as a 4 v 1 (it's not until 3 v 1 that the attacker's odds drop due to the loss of the third die).
Look what happens as a result of the first attack. Either you lose a defender or the attacker loses an attacker.
Case 1: you lose a defender. In the first case, you suffer a loss, but at these odds you really expect to. What happens next? Well the attacker advances all but one of his armies into the conquered country. So even though he "won" his strength has just been reduced by 1 army.
Case 2: attacker loses an attacker. Good for you, the attacker's strength has been reduced by 1 and now he has to go through another attack. The best the attacker can hope for on the second attack is Case 1. We know from case 1 that the attacker will lose a further army in the advance into the conquered country. So best case, the attacker will lose at least 2 armies, possibly more.
So the effect of the 3,1 defense is that even in the worst case scenario you have reduced the attacker's strength before he has to face your strongest defense. When I say strongest defense I'm not just thinking in terms of number of armies but how far you as a defender are away from crossing your thresholds. When I say the attacker's strength has been reduced I'm not just thinking in terms of number of armies but how much closer he is as an attacker to crossing his thresholds.
So, best case in conquering the first country the attacker loses an army (in the advance). Now let's consider the second country.
Here we have a 5 v 3 attack.
There are 3 cases for the outcome of the attack.
Case 1a: attacker loses 2 armies. Great for you because the attacker has just passed through one of his thresholds, he will lose one of his dice on the next attack.
Case 2a: attacker loses 1 army, defender loses 1 army. Leaves attacker with 4 armies and you with 2 armies. If the attacker loses an army in the next attack, he will lose one of his dice on the next attack.
Case 3a: defender loses 2 armies. Bad for you, now you lose a die for the next attack.
Remember if we were in a 3,1 defense the attacker would be facing these outcomes with an additional army cushion (i.e., he would be making this attack against our strongest defense with 6 armies instead of 5). That additional army cushion keeps the attacker away from crossing his thresholds and that's a bad thing for us, we want our attacker to be closer to crossing his thresholds -- we don't like the additional army cushion! Instead of the attacker being one army loss away from crossing his threshold in Case 2a he would be two army losses away from losing one of his attacking dice. Not a good thing!
The point is this: As the defender you want to put the attacker in a position where he is starting to cross his thresholds before you do. By putting one army up front (essentially a sacrifice) you whittle down the attacker's strength before he faces your strongest defense (the 3 in the rear).
In the 3,1 (front, rear) defense you allow the defender to attack your strongest defense at a point when his strength is the strongest. What that means is that he will be more likely to stay above his thresholds (which allow him to throw more dice than you) for the series of attacks against your strongest defense.
Finally, your last point is correct, a 3,1 defense is your best shot at not losing any territory, if that's what's really important to you. But presumably the overriding concern is to prevent you from losing your South America bonus. You've already lost your Africa bonus (if you even had it to begin with) because you're being attacked from Egypt.