I was under the impression that atwix often manages to lead subjects' armies. But perhaps I'm wrong. Sometimes it works for me, but most of the time it doesn't. It is very painful to have a large France under PU and to be absolutely unable to predict or even understand their behavior...
the rule on how to lead subjects and allies around is quite easy, once you understand the rules.
1. Subjects will never attach if not at war.
2. Subjects and allies will attach on owned, neutral or occupied terrain IF the combined unit weight of the stack is LESS then the supply limit of the province you are standing on.
Example: 3 units totalling 3000 on a 15 supply limit province can only hold 3+12 attached army without attached army fleeing the attrition.
3. You can give puppeteer stack a moving command THROUGH provinces the attached stack would take attrition (aka too few supply limit to sustain unit weight); what you gotta micro is that the TARGET province of the leading unit+attached army has to have more supply limit then the unit weight.
example: you can send 3k and a 27k ally (equalling 30 unit weight) army on the way to siege a 31 supply limit Ming province. On arrival, the attached stack will NOT flee to attrition, because unit weight is below supply limit. THIS is how you reliably siege with ally attached armies. Note that the attached stack won't flee to attrition WHILE ON WAY to the target province. They will arrive day later then you on any province, and re-attach until they reach destination.
4.
Most reliabale way of letting allies attach is to click attach to ally stack, press detach button, then vink the tickbox for "units an attach" on and off. This RESETS ally movement order, and forces AI to recalculate. They will then usually reattach, UNLESS ally has occupied provinces or rebels. If so, then they might refuse until that situation is dealt with.
5. Subjects Always attach, and if they don't on supportive, then switch them from supportive into "do what you want" back to supportive.
It is really that simple.
