I'd like to second Old Eagle's addition of Pike's PAVN to the list. I think it's worth mentioning that among other useful insights, the book presents a succinct and lucid explanation of what occurred in RVN during the period--1969 onward--about which less has been written.

PAVN employed a methodology to convince the populace of its implacability, and attempted to raise the level of violence (now perceived to be unending) toward an unacceptable threshold. A steady rhythm of assassination, indirect fire and sapper attacks, punctuated by "high points" of greater violence proceeded, despite great cost, even during the period of greatest US/GVN success (1970-71). The calculation was that the Vietnamese majority, who were not in the enemy camp, including those alienated by PAVN/VC overreach; the many ethnic Southerners in whom disgust at all Northerners, whether Communist or Catholic was an ingrained trait; and even the Northern Catholic denizens of the urban slums who had come South as refugees from Communism, would find submission to new, unsavory overlords preferable to endless bleeding. And in 1971 it had become clear that the Vietnamese would be bleeding alone--that the US was indeed withdrawing. Other grievances were eschewed, PAVN psyops concentrated on exploiting the war weariness.

The lesson to be drawn, Pike points out, is that in any society that is not totalitarian, there is no effective counter to the prospect of "the fifty year war."

Cheers,
Mike.