There are some significant differences in the environment in Pakistan today, compared to 2008.
The buildup to this attack has seen the Raymond Davis fiasco, the OBL raid, the Mullen rants, Hillary threats, and some major vilification of Pakistan in the Western media. Drone strikes have increased manifold since 2008, and they have also received correspondingly greater coverage and they have caused greater outrage.
In 2008 the military was also just recovering from the Musharraf years and the political parties were ascendant - that has reversed.
AM, with passage of time, new things happen. It is not like a vessel that is waiting to overflow. It is about management. Pacification of the general public is one crucial part of such management.
Increment in the number of drone strikes per year is no more a significant event than the allowance of such strikes. Public outrage at the first death of a civilian from a drone strike would be any time higher than the 1000th death, or increase in number of strikes.
About Mullen rants and Hillary threats, if they are significant in any way, then it is only because they are consumed by the people of Pakistan too. Such rants, and threats mean nothing in the seriousness of closed door talks and deals between the power-holders. Otherwise tell me, a Mullen rant, or a Hillary threat... can any time be bigger than Armitage saying to Mush that you better do it or we will bomb you to stone age?
Only difference is, words of Armitage were not heard by people of Pakistan. It was only the Army General who heard it, and he was pretty fine with it.
OBL raid is indeed a very very significant event, less because the US came so deep inside, more because the US in its own dirty way showed the world that "look, who was hosting the most wanted man".
The OBL raid was a much bigger problem for the PA, than for the people of Pakistan (who, much to the dismay of PA, came in the streets to show their solidarity for OBL). Yet, the PA did absolutely nothing, except for mincing the words - because it was content with the fact that within Pakistan, the PA was not demonized by the public.
Now AM, I will tell you about August 20, 1998. US wants Osama, hiding near Kunar/NW area. US warship comes to the Arabian Ocean, fires a Tomahawk, that lands in a Pakistani village, killing about 3 dozen villagers. Nothing in the news. No public drama. Clinton says sorry to Nawaz, who appears unexpectedly understanding of the situation and handles it very politely, in a mature fashion.
Way back in 1998, man it is bigger than OBL raid and any rants or threats or drone strikes. What does Pakistan say or do to the US? Nothing. Why? Because as long as people are not aware, it is all fine.
Well, it happens in all the countries, you only have to open your eyes. India does it, US does it, Pakistan does it too. Although I personally think that at this time, Pakistan has bit off a chunk tad too big for its throat. Americans do not only have a powerful Army, they also have a very powerful diplomatic, and economic force. And in these fronts, they are the masters of the world. PA should tread these waters more carefully.
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By the way, just found out, you were right about NATO not accepting the attack as deliberate. I just read the confirmation.