Kevin,

"So more arms caches have been discovered or disclosed in the South? What does that prove?"

Exactly what I said in the first place - In the Repulic of Ireland the IRA had, established and maintained it base of operations. Note when the IRA offered to show the authorities the grave sites of those they abducted, tortured and murdered - they took them South.

"Insofar as it was easier doing things on one side of the border and one side of the water rather than the other, that's presumably where they'd be done, but that's just operational details."

Again it supports precisely what I said.

"The point is, it's perfectly possible to carry on illegal and terrorist activity within the territory of the enemy and without a safe base elsewhere. And it reduces the problems involved in bringing explosives or personnel across borders, or across oceans."

Of course it is perfectly possible Kevin, but the risks that have to be run in operating that way increases the chances of being detected and caught.

"One of the main points of having a cell structure in a terrorist organisation is that it makes it possible to carry on autonomously if need be."

Yes Kevin but divorced from their command structure and the support it provides, any operations are severely limited. Activities by that cell to replace equipment or finance becomes more noticeable - i.e. attention gets drawn to certain activities occuring in a certain pattern.

"And that can have disastrous consequences for the victims."

The activities of "these hero's" nearly always has disasterous consequences for their victims - but to operate as you suggest fortunately also can result in disasterous consequences for the terrorists.