The Pakistan Navy operates a fleet of five diesel-electric submarines and three MG110 miniature submarines (SSI). Although these vessels are currently based at Karachi, it is possible that in the future some may also be based at Port Ormara. The nucleus of the fleet is comprised of two Agosta-70 boats and three modern Agosta-90B submarines, all of French design. Pakistan's third Agosta-90B, the S 139 Hamza, was constructed indigenously and features the DCNS MESMA (Module d'EnergieSous-Marin Autonome) air-independent propulsion (AIP) system. Pakistan began retrofitting the two earlier Agosta-90B vessels with the MESMA AIP propulsion system when they underwent overhaul in 2011.
The Agosta-90B Hamza (Khalid-class) was constructed at the Karachi Shipyard and Engineering Works (KSEW). Pakistani officials and media outlets extolled the accomplishment, treating the indigenous submarine's 26 September 2008 commissioning as a significant step in the enhancement of the country's naval capabilities vis-à-vis India. It is the first conventional submarine in the Indian Ocean to feature the AIP system (in this case a 200KW liquid oxygen MESMA AIP), which allows the vessel to increase its submerged endurance for up to 3 weeks and improves its stealth characteristics.
During the 1971 war between India and Pakistan, India effectively blockaded the port of Karachi, Pakistan's only major harbor. In response, Islamabad was able to curtail India's naval supremacy only through the use of its submarine force, which sank one Indian frigate. Drawing on these experiences and the perceived threat posed by a larger Indian Navy, Pakistan has been continuously investing in its submarine force, within the constraints posed by its economy.
An effective sea-denial capability is vital to Pakistan. Given that over 96 percent of this trade is seaborne, the Pakistan Navy and its submarine fleet is charged with protecting the country's sea lanes of communication (SLOC).
Developments in India's naval infrastructure and force posture significantly inform Pakistan's own naval planning. In February 2001, the Pakistan Navy publicly considered the deployment of nuclear weapons aboard its submarines, arguing that it had to keep pace with developments in India. Islamabad later rescinded its statement in January 2003, reaffirming Pakistan's commitment to a "minimum credible deterrence." In the wake of India's short-range Agni-I test that month, then Chief of Naval Staff Admiral Shahid Karimullah left the option open, saying that the country had no plans to deploy nuclear weapons on its submarines, and that it would do so only if "forced to." But most experts agree that Pakistan is, at the very least, attempting to develop a sea-based version of the indigenously built nuclear capable ground-launched 'Babur' cruise missile. This missile is similar in design to the American Tomahawk and Russian KH-55 cruise missiles.
Pakistan has explored options to purchase additional advanced diesel-electric submarines in an attempt to address the country's "critical force imbalance" with India, which plans to begin acquiring six French AIP-equipped Scorpène submarines at a rate of one per year in 2014. Discussions between the Pakistan Navy and Germany's ThyssenKrupp Marine Systems (TKMS) began in 2004 concerning the possible purchase of three diesel-electric Type 214 submarines equipped with an AIP system based on fuel cell technology. Although the deal appeared close to completion in 2008, it stalled over financing concerns and German political opposition to fueling an arms race in South Asia. Parallel to the negotiations with TKMS, France also attempted to sell its Marlin or Scorpène-class submarines to Pakistan, and revived discussions after Pakistan failed to finalize the contract with Germany. In May 2011, the Pakistani cabinet approved the start of negotiations with China over the purchase of diesel-electric submarines equipped with AIP.