My irregular tactics:Originally Posted by TheFlemishDuck
I divide the 15-20 divisions into commands of 3 divisions each. More than 3 will increase attrition too much.
For Punjab - I typically send 6 divisions (2 groups of 3) for the first border province attack, and then reinforce with an extra 1 group (3 divisions) once my initial wave starts to tire. Then a few divisions around the northern rim of the country, where the provinces are lightly guarded if at all. Simultaneous advances from the north and south let you attack any concentrated buildups from two divisions.
The tough battles with Punjab are in the first province and then in the capital. After you win those, the rest of the invasion is cake because the existing Punjabi forces never have time to recover their organization or morale. Even through your forces are suffering attrition, as long as they are winning battles, cleanup is pretty easy after you get the border province and the capital.
I didn't really pay much attention to whether the Punjabis reinforced or not. I think they probably did. This can work to your advantage because reinforcing an existing division can completely destroy its organization, reducing it dramatically, even to zero. Hit them once, twice, and plow through the country while stopping to take no prisoners. Don't let the Punjabis sit around and regain organization after reinforcing. The key to warfare with irregulars, as you have mentioned, is speed, as the troops don't have the endurance for sustained warfare. With speedy attacks, I have repeatedly been surprised that Punjab is annexed while my irregular divisions still have most of their manpower left.
Afghanistan of course is easier because they have (IIRC) fewer troops. They do have one leader, I think, but not a stellar one, and often he is only in control of one division and can easily be encircled and destroyed.
Of course Tibet has enough manpower that you can easily get forty, fifty, sixty divisions of irregulars if you have any concerns about the chances against Punjab. The real trouble initially is that I find it hard to get more than 30 regular clothes (for converting pops to soldiers in VIP) off the early market in a reasonable time period within the first year.