In the 1990s, the navy lost its opportunity to equip itself with latest technology and negotiated with the Royal Navy to acquire ageing "Tariq"-class destroyers in 1993–94, which continue to be extensively upgraded. During the same time, the Navy engaged in a process of self-reliance and negotiated with China for assistance. This ultimately led the introduction of F-22P "Zulfiquar"-class frigates, which were designed and developed at the Karachi Shipyard and Engineering Works (KSEW); at this same time, the "Agosta"-90B submarines were also built. Pakistan's role in the War on Terror led to a rapid modernisation, which saw the induction of the PNS "Alamgir" anti-submarine warship in 2011. The submarines remain to be backbone of the navy, which has been developing a nuclear submarine. Since 2001, media reports have been surfaced that the Navy has been seeking to enhance its strategic strike capability by developing naval variants of the nuclear cruise missile. The Babur cruise missile has a range of and is capable of using both conventional and nuclear warheads. Future developments of Babur missiles include capability of being launched from submarines, surface ships, and a range extension to . An air-launched version, "Ra'ad", has been successfully tested.