Ine Givar IMTU:
They are a collection of the disaffected, the Zho Symps (gotta put me one in there called Berka
), and some general malcontents, interspersed with a few SORAG agents. They were smaller before and after the FWs and creep up a lot during the FWs as the Zhos pump some bucks in to making them a pain in the Empire's midrift. Of course, when the war abates, the Zhos throttle back spending and the cells either go rogue or go dormant until the next episode.
So during peacetime, they're a low level threat, with enough impact to keep the name out there. They bomb some stuff, make some people disappear, etc.
In my current campaign, a cell on Inthe is trying to acquire bioweapons (and failing, thanks to the players who decided to sell them back to SuSag). They'll show up again as an on-going menace, since they now have an axe to grind with the PCs if they get the chance (at least that cell does).
I think during wartime, they escalate - they have more SORAG agents infiltrated, more money funnelled in, arms funnelled in, cadre... and the net effect is greater degrees of coordinated activity.
BTW, the IRA have been called a guerilla army. Michael Ignatief has done some good work lately in analysing the ethics of strong vs. weak conflicts and asymetric warfare and how this pertains to rules of war and human rights. I'll leave the details for you to investigate
But they are clearly not a GORILLA army. That'd require geneering, though it probably is possible (a la Planet of the Apes) in Traveller.
Oh, and an even better take on Star Wars and Rebel Scu...err.... Heroes:
The Case For The Empire