As readers of these posts know, DBT stands for the Drive-By Truckers, whose music has been extolled here repeatedly. Consider this a not-so-subtle plug for additional entries for the ACW holiday competition for best lyrics about the Bomb.

DBT also stands for Design-Basis Threat, an essential planning device to protect sensitive sites against unauthorized, heavily armed entry. Design-Basis Threat calculations help the home team figure out how much and what kind of protection is needed against outsider threats until the cavalry arrives. If the outsiders are many in number, well-armed, and helped by insiders, the cavalry has to come quickly.

The biggest current worry for Pakistani authorities in DBT calculations isn’t the Haqqani network or Lashkar-e-Taiba. The former has trained its sights on U.S. and NATO forces in Afghanistan and the latter is focused primarily on India — at least for now. The biggest headache for the Pakistan military at present is the Tehrik-e-Taliban Pakistan.

The TTP is an umbrella, mutating group of clans and tribal fighters that coalesced in 2007 after President Pervez Musharraf ordered Army units to seize control of the “Red Mosque” in Islamabad, whose clerics were openly defying the state. A ten-day siege resulted in approximately 100 deaths, prompting a war of vengeance against the Pakistan military. Baitullah Mehsud, the TTP’s initial leader, was killed by a U.S. drone strike in August 2009. A fellow clansman, Hakimullah Mehsud, has taken his place. His tenure may be shaky.

The TTP’s home base is in the tribal lands of Waziristan, but its reach extends all over Pakistan. It has been implicated in the December 2007 assassination of Benazir Bhutto in Rawalpindi, the September 2008 truck bombing of the Marriott Hotel in Islamabad, and even the failed Big Apple Times Square bombing in May 2010. The TTP may also have carried out attacks on Army headquarters in Rawalpindi (October 2009), the Mehran Navy base in Karachi (May 2011), and the Kamra Air Force base in the Punjab (August 2012).

Attacks on Pakistani military installations have raised fears about the security of Pakistan’s nuclear assets. I’m not convinced that these attacks have been primarily about nuclear weapons. In my view, they seem designed to lay down markers and embarrass Rawalpindi. The attacking forces in these cases – less than two dozen men armed with automatic weapons and rocket-propelled grenades – have been capable of damaging military equipment and holding out for a long news cycle, but no more. When Pakistani commandos arrive on site from nearby locations, these attacks become suicide missions, sooner or later.

Compare the attacks on Kamra, Mehran, and Army HQ with the jailbreak in the town of Bannu, 120 miles south of Peshawar in April 2012. Over one hundred TTP fighters were reportedly involved, armed with explosives, rocket-propelled grenades, and automatic weapons. They demolished the front gates and blew gaping holes in two walls of the prison. A jail population is, by definition, the ultimate insider threat. By the time the cavalry arrived, two hours after the attack began, 384 prisoners, including more than 20 extremely hard cases, escaped. A successful operation on this scale against a sensitive Pakistani military base cannot be discounted, but would be extremely difficult for Pakistani extremists to pull off.

The attacks on Army HQ, Mehran, and Kamra were not random acts. They came after intensified Pakistani military operations against the TTP and, in the case of the Mehran attack, after the raid by U.S. Navy Seals that killed Osama bin Laden. Future attacks might follow this pattern.

The organization responsible for physical security at sensitive sites in Pakistan, the Strategic Plans Division, can be expected to continually update its DBT calculations. The Drive-by Truckers would be on board. As their tune, “Purgatory Line,” observes, “This ain’t exactly Hell. [And] it sure as hell ain’t heaven.”