CHANGES IN ANTI-SUBMARINE WARFARE: The anti-submarine arena has changed in the last decade, due to several factors:


@ There will be no deep water anti-submarine battles in the North Atlantic. The Russian Navy, desperately short of cash, simply cannot sustain such a campaign.


@ Regional navies are now using ultra-quiet conventional submarines with Air Independent Propulsion (AIP), subs which are vastly harder to track than older nuclear boats. The advent of AIP has reduced the time a conventional submarine must spend snorkeling, often by 80% during critical periods when conflict is most likely.


@ Western governments are increasingly unwilling to tolerate casualties in an attrition war, and are increasingly reluctant to try to shoot their way into defended areas when conditions are not in their favor. 


@ The focus of future conflicts has shifted to areas such as the Yellow Sea, the Persian Gulf, and the Timor Sea. These areas feature shallow water, plenty of noise from passing ships, and other conditions (hot water in the Gulf, rocky bottoms in other areas) which make sonar considerably less effective than it is in open ocean.


@ Operational exercises, and computer simulations, have shown that modern submarines operating in shallow water can inflict far higher losses on the surface ships trying to destroy them than submarines in the open ocean can expect to achieve. 

@ New low-frequency sonars can penetrate the rubber tiles that coat modern submarines, but also give a high false alarm rate due to reverberation.


@ The best hope for a technology able to deal with the new submarine threat is a multi-station sonar system. By using several different transmitters and receivers at widely separated locations, signal patterns might be pulled out of the clutter by vast arrays of high speed computers.--Stephen V Cole