Antisubmarine Warfare (ASW)

Warfare designed to combat submarine threats and to maintain naval dominance. Antisubmarine warfare (ASW) comprises both technology and tactics used in combating enemy submarine power. The U.S. Navy historically has focused a great deal of its resources on developing innovative ASW to respond to the continual challenge of new enemy submarine technology.

During World War I, the submarine was able to menace merchant vessels. The first ASW strategy against German submarines was to ship supplies in a convoy. Following the war, to prevent submarine attacks, active sonar was developed by the British. When coupled with depth charges, active sonar provided the navy with the capacity to destroy enemy submarines.

During World War II, however, German submarines began attacking on the surface, often as a group using “wolf pack tactics” to counter ASW tactics. As both the ASW sonar technology and the tactic of shipping by convoys proved ineffective for the Allies, long-range aircraft were outfitted with radar and used as escorts. In addition, new electronic and communications intelligence was able to protect the convoys by locating German U-Boats (submarines). New technological developments, such as sonobuoys, acoustic homing torpedoes, magnetic anomaly detectors, and microwave radar, also played a significant role in combating the submarine threat during World War II.

Technological developments were not limited to ASW. At the start of the Cold War, Soviet advances in submarine technology represented a serious threat to U.S. naval power. These advances, coupled with submarine technologies adopted from the end of the war, allowed the submarine to travel longer underwater, thereby evading detection.

The ASW policy during the Cold War differed from previous policy in that emphasis was placed on developing countermeasures before the enemy could develop its own technological advancements. Therefore, in anticipation of new submarine developments on the Soviet side, the United States placed an unprecedented focus on ASW. Not only were improvements made to existing ASW, but also a new ASW submarine (SSK) was developed, along with the passive acoustic array.

The later emergence of the Soviet nuclear submarine provided another challenge to ASW strategy. Developments in U.S. nuclear submarines illustrated the danger that would exist when the Soviet Union adopted the new technology. However, the new nuclear submarines did have a weakness: the amount of noise they produced. Therefore, research and development worked to create quieter submarines and better sonar to solve and exploit the problem.

The focus was placed on passive sonar, which was most effective against the nuclear submarine. By the mid-1980s, however, the Soviets had developed a quiet nuclear submarine. In response, the U.S. Navy had to rethink its focus on passive sonar and explore other avenues. Fortunately for the United States, the demise of the Soviet Union in 1991 meant that the United States had been given a reprieve from the battle between these new, quieter subs and ASW efforts.

Although the Cold War has ended and Cold War antisubmarine warfare was effective, there are new challenges to meet in the future. The current posture of the U.S. Navy is different from its previous strategy—control over the seas and ASW are no longer its top priorities. However, new nonnuclear submarines have been developed that do not have the same weaknesses [Page 28]as previous submarines and for which ASW tactics and technologies already exist. The increasing ease of obtaining these technologically advanced submarines will most likely present a significant post–Cold War challenge to antisubmarine warfare policy and strategy.

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