This is the piece of the wikileaks documents that has gotten the most coverage, I think:

Pakistan Aids Insurgency in Afghanistan, Reports Assert – NYTimes.com

Americans fighting the war in Afghanistan have long harbored strong suspicions that Pakistan’s military spy service has guided the Afghan insurgency with a hidden hand, even as Pakistan receives more than $1 billion a year from Washington for its help combating the militants, according to a trove of secret military field reports made public Sunday.
….
The records also contain firsthand accounts of American anger at Pakistan’s unwillingness to confront insurgents who launched attacks near Pakistani border posts, moved openly by the truckload across the frontier, and retreated to Pakistani territory for safety.
….
The reports suggest, however, that the Pakistani military has acted as both ally and enemy, as its spy agency runs what American officials have long suspected is a double game — appeasing certain American demands for cooperation while angling to exert influence in Afghanistan through many of the same insurgent networks that the Americans are fighting to eliminate.

A few points:

(1) What is new is not the suspicion that Pakistan may be aiding the insurgency.  What is new is that this assessment is not just held by anti-war critics, but also by people inside the U.S. military. I have no way of confirming this assessment, nor judging how widely held this assessment is.  But if this is a broadly held consensus, it is significant for at least two reasons.
(A) It shows that various outside analysts were quite close to the mark in terms of the problem posed by Pakistan’s search for “strategic depth” in Afghanistan.  This goes beyond the insurgent sanctuary problem, but also confirms its existence. There has been a lot of wishful thinking about our ability to essentially isolate Afghanistan as a battlefield, and insufficient consideration of the consequences for the conflict, if, in the final analysis, it is impossible to eliminate the insurgent sanctuary in Pakistan.  That said, some of these documents are old, and it is unclear how much has changed on this issue in the meantime.
(B) Again, if these documents paint an accurate picture, it reveals a troubling disconnect between public pronouncements and private assessments.  Ultimately, democratic governance and accountability requires giving the public sufficient information to make informed decisions. Keep doubts and concerns private may serve legitimate strategic objectives, but we need to acknowledge that our strategic objectives in Afghanistan may be at odds with the requirements of democratic governance at home.  In short, is it ever worth fighting a war that requires your to compromise and weaken accountability at home?

(2) The United States clearly needs to make some tough choices with regard Pakistani interests in Afghanistan.  My assessment has long been that Pakistan perceives that it has compelling national interests at stake in Afghanistan.  Though my assessment is that many of these “interests” are in fact illusory — notably the “strategic depth” concept — my assessment is wholly irrelevant.  Unfortunately, it is my impression that American policy has been too heavily reliant on the notion that we might ultimately be able to talk Pakistan around to a more “reasonable” assessment of their interests on the ground.  Again, it is possible that circumstances have already changed, but on the whole it strikes me as more likely that Pakistan perceptions represent a durable assessment of strategic interests, and that as a consequence American policy needs to be pursued based on a clear-eyed view of how the Pakistanis seek Afghanistan rather than how we would wish to see it.  The consequence of this assessment is to push American thinking toward the achievement of minimalist goals, since at least some of our maximalist agenda in Afghanistan is likely to be in conflict with Pakistani preferences.

(3) I think it remains unclear whether Pakistan is ultimately a source of encouragement or of restraint vis-a-vis the Afghan insurgency.  It is likely elements of both.  But I think it is a mistake to assume that Pakistani involvement with the insurgent — if an accurate judgment — is necessarily fundamentally at odds with American interests — even if it at odds with American strategy.  In short, I think it is reasonable to ask whether Pakistani involvement with the insurgency might not prove to be a source of leverage were we the reconceptualize our approach around seeking to managing Afghanistan rather than “win.”

(4) The political consequences of these leaks are likely to be massive.  U.S.-Pakistani relations are going to hit a very rocky patch.  Key now is to think about the long-run.  But there will be a lot of demands for ratcheting up pressure on Pakistan, which is likely, I think, to be counter-productive.

I’ll be writing more about these documents today and tomorrow.