were deployed with high-speed anti-shipping missiles. Previously believed to be interceptors of NATO supply convoys traveling the sea lines of communication across the North Atlantic Ocean between Europe and North America, the primary role of these aircraft was to protect the Soviet mainland from attacks by U.S. carrier task forces. Submarines Due to the Soviet Union's geographic position, submarines were considered the capital ships of the Navy. Submarines could penetrate attempts at blockade, either in the constrained waters of the Baltic and Black Seas or in the remote reaches of the USSR's western Arctic, while surface ships were clearly much easier to find and attack. The USSR had entered the Second World War with more submarines than Germany, but geography and the speed of the German attack precluded it from effectively using its more numerous fleet to its advantage. Because of its opinion that "quantity had a quality of its own" and at the insistence of Admiral of the Fleet Sergey Gorshkov, the Soviet Navy continued to operate many first-generation missile submarines, built in the early 1960s, until the end of the Cold War in 1991. In some respects, including speed and reactor technology, Soviet submarines achieved unique successes, but for most of the era lagged their Western counterparts in overall capability. In addition to their relatively high speeds and great operating depths they were difficult anti-submarine warfare (ASW) targets to destroy because of their multiple compartments, their large reserve buoyancy, and especially their double-hulled design. Their principal shortcomings were insufficient noise-damping (American boats were quieter) and primitive sonar technology. Acoustics was a particularly interesting type of information that the Soviets sought about the West's submarine-production methods, and the long-active John Anthony Walker spy ring may have made a major contribution to their knowledge of such. The Soviet Navy possessed numerous purpose-built guided missile submarines, such as the , as well as many ballistic missile and attack submarines; their are the world's largest submarines. While Western navies assumed that the Soviet attack submarine force was designed for interception of NATO convoys, the Soviet leadership never prepared their submarines for such a mission. The force also targeted American aircraft carrier battle groups. Over the years Soviet submarines suffered a number of accidents, most notably on several nuclear boats. The most famous incidents include the , and the Komsomolets, both lost to fire, and the far more menacing nuclear reactor leak on