Shashank Joshi has a good rundown of the strategic implications of the Taliban attack on PNS Mehran. The only part I'm uncertain about is this:

Thirdly, the attack's terrible human toll was accompanied by the highly visible, and militarily significant, destruction of at least one, perhaps two, P-3C Orion anti-submarine and maritime surveillance aircraft (one has been destroyed; two others appear damaged). These $35m US-supplied aircraft - advanced variants of the older P-3 aircraft - were inducted last summer, with the expectation that six more would follow by 2012.

 

Their loss compounds an already lopsided naval balance with respect to India, which now possesses twice as many submarines, and five antisubmarine warfare squadrons. In the first place, this prompted some to ask, in conspiratorial tones, why the Pakistani Taliban would attack such a site, and whether 'foreign agents' might be the more likely perpetrators of an attack whose beneficiary would be India. Although increasing numbers of Pakistanis recognise internal militancy as a serious threat to the country, the peculiar nature of the target may reinforce the self-destructive narrative that violence in Pakistan is the product of external meddling rather than internal rot. But the longer-term military implications are also important.

 

These may seem of little relevance in an age in which nuclear deterrence has tightly constrained the scope and intensity of Indo-Pakistani wars (see, for example, the enormous limits on escalation during the 1999 Kargil War). Does anyone really envisage a naval war, except as part of an all-out war in which third parties and their navies would be anyway engaged? But this perspective ignores that India might, in the aftermath of a future crisis, view a naval blockade as a suitably calibrated response that applies pressure on Pakistan without crossing nuclear thresholds. [3] Pakistan's now degraded anti-submarine warfare capabilities may prove to be of more than symbolic value.

If I recall correctly, the P-3Cs were being used by Pakistan as COIN patrol craft, rather than in their ASW role. Thus, the destruction of the P-3s might have less to do with a symbolic attack on Pakistan's naval capability and more with a direct attack on Pakistan's COIN capability.

 

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It does make one wonder about the integrity of the Pakistani nuclear weapons storage.

From Economic Times

 

[excerpt]

 

24 May, 2011, 09.52AM IST, Chidanand Rajghatta,TNN

Three Pakistan nuclear sites attacked in last five years, says expert

 

WASHINGTON: It's a subject Americans can't stop discussing and one Pakistan hates talking about. The Mehran attack has once again focused world attention on the security of the country's fast-growing nuclear arsenal. ...

 

Pakistani militant attacks over the last five years include strikes against three nuclear facilities, in Wah, Sargodha, and Kamra, according to Prof Shaun Gregory, a security specialist at Bradford University. But each time, the Pakistan military establishment, which has itself suffered attacks at its General Headquarters and training and recruitment centers , insists that there was no danger to its nuclear assets. ...