The American Los Angeles class nuclear attack submarines (SSN) were built in the Cold War to fight the Soviet Navy SSNs like the Akula, Victor and the Sierra classes. With their superior stealth, advanced spherical sonars and fast speed, the Los Angeles class (688 class) and the improved Los Angeles (688i) dominated naval warfare below the surface, against ever more advanced Russian submarines. They preserved the US Navy’s underwater edge in the last couple of decades of the 20th century.