Hi, my name is Francis, and I'm a Rules Lawyer...
OK, here's the situation: your disrupted BG of 5 bases is fighting 2 enemy BGs: 2 bases fighting BG 'X' at factor 'a', 2 fighting BG 'Y' at factor 'b', 1 base fighting 'Y' at factor 'c':
XYY
abc
ab-
You lose 1 dice per 3. For 5 dice you just lose 1. The question being, which dice can you lose: a, b, and/or c?
After periods of deep introspection, reading other posts on the subject, consulting the Oracle at Guinness, and, *gasp*, reading the rules, I've decided that you have no choice: you must lose 1 of your 3 dice against BG Y, and it must be at factor 'b'.
I will admit that the rules on p. 94 are not as clear as they could/should be. What is (relatively) clear IMO is that you can not lose the lone 'c' dice, based on the 2nd bullet on p. 94 which says "If fighting at different POAs... [leave] at least 1 dice (if possible) against each part of the enemy BG".
The argument that you must lose your dice against BG Y and not X is more tenuous, but basically rests on assertions that a) it best follows the spirit of the rule (and works well in practice), and, b) to permit otherwise leads to patent silliness. More specifically, I would argue that if part of your combat dice can be apportioned evenly, they you can (and must) apportion lost dice within that part, without regard for what is happening in the wider combat. In the example above, since you have 3 dice against BG Y, and you lose 1 dice per 3, you *automatically* lose 1 and only 1 dice against BG Y, irregardless of whether or not other parts of your BG are fighting elsewhere and with what number of dice. The alternative - that even though normally you would lose 1 of 3 dice against Y, that instead you can lose 0 or 2 because of the circumstances of the wider battle - is a recipie or silliness or even abuse.
Thanks for listening

