Ernie – I'm absolutely happy with the conclusion that Pakistan is behind the taliban insurgency. What I'm not clear about is that it makes sense for Pakistan to back the taliban so that they can actually win. Pakistan (and I'm indebted to Stephen Tanner for explaining this properly) has always sought what they call "strategic depth" in Afghanistan as insurance against an invasion of Pakistani territory by India. Because Pakistan is rather narrow, especially around Islamabad, and has its back up against the Suleiman range, and because India's conventional forces are both hugely larger and hugely superior, Pakistani strategists covet the ability to retreat into/across the Suleimans through the Khyber and Bolan passes into reasonably friendly territory. The ideal situation is one in which the passes are permeable for a retreating Pakistani force, but not for the Indians.
However, an Indian invasion of Pakistan is vastly less likely (a) while there are substantial US forces in Afghanistan and (b) while Pakistan is able to cosy up to the US as a key ally in the WoT. Pakistan has benefitted massively from US support since 2001, in finanical and aid terms and also in military assistance. While I absolutely agree that Pakistan wants their preferred regime in Kabul and has the creeping horrors of one sympathetic to India being in power, they don't have any immediate interest in getting massively on the wrong side of the US.
