No problem, here goes...
If you have a combat involving more than two units (ie. two of your units engaged with one enemy unit, like you said), it is all worked out as one big combat. So you would add up the total number of wounds inflicted on the enemy by both your units, and the enemy would add up the number of wounds they caused on each of your units as well.
Then, after adding in all of the other CR bonuses you and your enemy are each entitled to, you compare the grand totals for each
side (not each unit), and whoever's total is larger, wins the entire fight.
After that,
every unit on the
losing side must take a break test. Although if some losing units pass the test, then they remain in combat and fight on (meaning that if your units are still in base contact with any enemy that held, they cannot pursue the enemy that fled. Only those of your units that are no longer in base contact can pursue fleeing enemy).
There are a couple of other things to know about when working out a combat involving multiple units;
- First, when adding in your rank bonus, you only add the ranks from your biggest unit (ie. the one with the most ranks). You
do not add the rank bonus from each of your units. Also, I forgot to mention something about the rank bonus. The rank bonus is the only thing that you claim for
before the fight starts, all other CR bonuses (including wounds and outnumbering) are claimed for
after the fight has ended. So you can start with and claim a full +3 rank bonus before any attacks are made, even if your unit falls below the numbers required to claim a full bonus when the fight has ended.
- For the outnumbering bonus, you add up the unit strength of
all your models that are involved in the same fight. The enemy does the same and whoever has the largest total unit strength gets the bonus (obviously, if the totals are equal, no-one gets the bonus).
- As I said before, when adding the +1CR for having a banner, you only get a maximum of +1
for having a banner,
not +1 for each banner.
Also, don't forget that if a unit has been engaged in the flank or rear, they lose their entire rank bonus. Although for this to happen the enemy unit in their flank/rear must be unit strength 5 or more and not be skirmishers.
As you can see, hitting the enemy in the flank is highly desirable, since it removes their rank bonus and also gives your side +1 for attacking the enemy flank (or +2 for the rear). Contrary to the rule above, even skirmishers can claim the flank/rear bonus, but whoever is in the flank/rear must still be unit strength 5 or more.
I hope you can follow all that! It can be quite complex (even I got it wrong for a long while!), I suggest you print this out and run through a few test combats to get the basic idea. You could also make up a few check sheets with all the bonuses listed and when working out the combat, you can tick each bonus off and add it all up at the end.
As always, feel free to ask if you have any more queries.