Sauro-class submarine
The "Nazario Sauro" class are diesel-electric submarines operated by the Italian Navy. All boats were built by Fincantieri in Monfalcone. History. Italy developed the Sauro-class submarines in the 1970s to counter the underwater threat of the Soviet Union. Italian shipbuilding company Fincantieri built these vessels in Monfalcone. The class entered service in 1980 and replaced the mixed fleet of Toti, Tang and Tench class submarines. A further two units, "Leonardo da Vinci" and the "Guglielmo Marconi" were commissioned in 1981 and 1982. In 1983 and 1988 two additional pairs of boats were ordered to the  Improved Sauro class design. They were delivered in 1988-89 and 1994-95 by Fincantieri. They were eventually succeeded by the Todaro-class (the joint German-Italian Type 212-based group). "Sauro" and "Cossato" were Batch I boats while "da Vinci" and "Marconi" were Batch II boats. "Pelosi" and "Prini" made up Batch III and "Longobardo" and "Priaroggia" were the two Batch IV boats. Lengths varied between the batches. Beams measured 6.8 meters for all of the class. Draught was increased progressively from 5.3 meters to 6.3 meters. Armament of all the batches was 6 x 533mm torpedo tubes  with 12 reloads carried. Batches I and II used Whitehead A-184 torpedo series while batches III and IV used upgraded Whitehead A-184 Mod 3 series. The Sauro and Marconi were retired in 2001 and 2002 respectively. In 2005, the remaining two original submarines were retired and the remaining four, the "Salvatore Pelosi" (S522), "Giuliano Prini" (S523), "Primo Longobardo" (S524), and "Gianfranco Gazzana Priaroggia" (S525) were upgraded. These upgrades included replacement of the acoustic sensors and weapons control system, improvements in the communications system, and extension of the service lines. US approached Italy to purchase retired Sauro-class submarines. Italy tentatively  agreed but Taiwan rejected the offer. The plan called for the US to purchase four submarines when decommissioned, then refurbish them in the US and sell them to Taiwan. Once refurbished, the Italian submarines were expected to be operational for another 15 years, and the deal included an extension program. Design. There are three sub groups built in four batches: