The U.S. Navy believes it has developed new tactics, and technologies, that can defeat the quiet, and deadly, diesel-electric submarines it may have to fight off the coasts of hostile nations. China, North Korea and Iran all have such subs, and have made threatening noises towards the U.S. Navy. The new approach uses air dropped sensors, equipped with computers and radio communications, to make a combat zone less suitable for diesel-electric subs to hide in. These boats, while quiet, do make some noise. The new sensors, similar to the familiar sonobuoys, would silently collect information, do a lot of the processing (to separate the passing whales from passing subs), and then quickly (and in a hard-to-detect fashion) transmit the information to American ships and aircraft. Details of the new sensors are, naturally, secret, and will remain that way for as long as possible. The new devices are far more capable than the sonobuoys that aircraft (like the P-3) and helicopters have been dropping for decades. The more information potential enemies have on the new sensors, the more likely they can find ways to make the sensors less effective, or not effective at all. The new sensors will be tested against diesel-electric subs belonging to allies. The Australians have been very active in these exercises, and an even more advanced Swedish sub, with an AIP (Air Independent Propulsion), has been leased, along with its crew, for training exercises. China, North Korea and Iran have, for the most part, older and noisier diesel-electric subs. But even these boats are quieter than most nuclear subs (which have to run pumps at all times to circulate cooler water around the hot nuclear reactors). We may never know for sure how well this new approach will work, just as we never got to find out how the Cold War era tactics for fighting Russian nuclear, and diesel-electric subs, would have worked. But there were plenty of situations where American subs, and ships and aircraft got to actually stalk Russian subs, doing everything they would do in wartime, except for launching weapons against the Russian boats. Those exercises wont be repeated as often, if at all, with the new tactics. You dont want to drop those new sensors somewhere where you cant get them back. Then again, who knows.