The USS Trigger (SS-564) was a Tang-class attack submarine of the United States Navy, notable for its engineering modifications and operational history during the Cold War era. Laid down on 24 February 1949 at Groton, Connecticut, by the Electric Boat Company, she was launched on 14 June 1951 and commissioned on 31 March 1952. The vessel measured approximately 314 feet in length, with a beam of about 28 feet, and displaced around 2,880 tons when surfaced. Her initial propulsion system consisted of four high-speed diesel engines, which were later replaced by three medium-speed engines during a major overhaul in 1958 to improve reliability and maintenance. Trigger’s early service included shakedown training off Rio de Janeiro and operations along the East Coast of the United States, culminating in participation in Arctic exercises and NATO operations such as "Strikeback" in 1957. In 1958, she underwent significant modifications, including being lengthened by nine feet to accommodate her new engines and later, in the late 1960s, further hull lengthening to install PUFs sonar equipment. Her service record includes deployments with the Sixth Fleet in the Mediterranean, notably in 1962, 1964, 1966, and 1969, where she conducted various patrols and exercises. In 1970, Trigger transferred to the Pacific Fleet, arriving in San Diego and participating in testing exercises like the Mk 48 torpedo trials. Her operational scope extended to the Western Pacific, including deployments to New Zealand, Australia, and Asia, with participation in joint exercises and special submarine operations. She played a role in training the Italian Navy’s crew before being decommissioned and transferred to Italy on 10 July 1973, where she served as Livio Piomarta until her decommissioning in 1986. Trigger’s extensive operational history, modifications, and Cold War deployments highlight her significance as a versatile and resilient submarine in the US Navy’s fleet during her service life.

This description has been generated using GPT-4.1-NANO based on the Vessel's wikidata information and then modified by ShipIndex.org staff.