SSN (hull classification symbol)

An SSN is a nuclear-powered general-purpose attack submarine. SSN is the US Navy hull classification symbol for such vessels; the SS denotes a submarine and the N denotes nuclear power. The designation SSN is used not just in the United States Navy (USN), but throughout NATO under STANAG 1166.

The first nuclear-powered attack submarine was the US Navy's USS Nautilus, operational from 1954. This was followed by the four submarines of the Skate class entering service in 1957. The Royal Navy's first nuclear fleet submarine was HMS Dreadnought which by using an American reactor entered service in 1963. The first all-British nuclear submarines were the two Valiant-class submarines.

The USN submarine fleet has been all-nuclear powered for over two decades. The bulk of the USN's SSN fleet has been the Los Angeles-class attack submarine. Designed during the Cold War the Los Angeles-class boats' raison d'etre was to protect USN carrier battle groups and to hunt Soviet Navy SSBNs before they could launch a first strike against the United States.

The first ever major combat action involving an SSN was during the 1982 Falklands War. An Argentinian cruiser, ARA General Belgrano was sunk by torpedoes fired by the Royal Navy fleet submarine HMS Conqueror. After that incident, the Argentinian Navy was effectively confined to port.

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