It's just a regular disengage/withdraw into a units flank or rear, followed by a fire attack. It happens with regular units, too, however, these can only assault, not fire,and since this usually happens right after you attacked their flank/rear, assaults aren't much to fear (and not something the AI will usually risk, as morale will be low). It will shoot, however, and that flanking fire will have quite an effect on morale, even if the shooting unit has low morale and high disruption.
(Depending on how your units are set up, it is also possible to have a ZoC gap in the middle of your line - at a salient, for example, through which one could then advance by disengaging... but you pretty much have to set that up on purpose for it to happen, normally this happens only with units not in/on the end of a continuous line.)
The result is that while it is clearly preferable to flank regular units, it can often be preferable to attack frontally vs skirmishers even when you can flank, because the damage you take that way is less than what you'll take when you suddenly find them on your flank due to a disengage/withdraw.
Combine that with the fact that all it needs is one rally point to turn a routed unit of skirmishers behind your own lines into a serious annoyance, and there's room for a whole lot of gamey tactics. And while the AI generally isn't all that smart, it tends to really make the most out of such situations...
(I can easily live with irregulars not being destroyed, merely "driven off" by a determined attack, but if they rally again after that, they should do what irregulars did when they found themselves behind enemy lines - look for the camp and baggage and start some looting, not return to the fray with a vengeance, and more effective than before.)
< Message edited by jackx -- 7/8/2009 7:35:07 PM >
no truth - no justice
all false belief
blinded by morality
there shall be ... no peace