WASHINGTON, April 28 (UPI) -- Anyone who has watched any World War II movies or History Channel documentaries knows what a wolf pack was: It was the massed attack carried out by Nazi submarines against British and American convoys of merchant ships in the Battle of the Atlantic during World War II. China is looking at a modern, 21st century of wolf pack tactics for any future war it might have to fight against the United States. But the wolf packs and their tactics would be very different.

German U-boats in the 1939-43 Battle of the Atlantic were remarkably small, slow and fragile boats by modern sub standards. Even at the time, they were totally outclassed by the much larger, longer-range and more effective fleet submarines the U.S. Navy used against Imperial Japan. But they were still a formidable strategic weapon and in 1942-43 they came dangerously close to winning the war in Western Europe for the Third Reich by nearly cutting off Britain's Atlantic lifeline of supplies sent by ship from North America.

The Nazi wolf packs were faster than slow-moving convoys of cargo ships, however, when they surfaced. So wolf pack attacks were not launched from underwater, or by day. They were carried out on the surface of the Atlantic by night. The aim was to have so many submarines that they could overwhelm the smaller number of surface escort warships protecting the merchant vessels.

The new tactical concept of the Chinese wolf pack that could threaten U.S. aircraft carrier task forces in coming years, however, is very different. Modern diesel-electric submarines can stay underwater for long periods of time and can travel fast in spurts of speed, though they don't have the endurance of nuclear-powered subs. That speed means they don't have to surface where they would be easy targets for carrier-launched aircraft. And they don't have to await for any attack by night either.

So any attack by the diesel-electric Kilo or Sung class submarines of the Chinese navy against U.S. carrier battle groups operating in the Central or Western Pacific could occur at any time in the day or night, and their goal wouldn't be to just sink cargo ships like the German Kriegsmarine subs of World War II. They would be loaded for bear: They would be out to kill 90,000 ton nuclear-powered super-aircraft carriers.

However, the same basic wolf pack concept would apply. China is building large numbers of cheap, easily constructed diesel-electric subs in the hope that if a naval war with conventional weapons had to be fought in the Pacific, their subs could overwhelm U.S. anti-submarine warfare defenses by sheer weight of numbers.

China's diesel-electric subs have other advantages going for them besides sheer weight of numbers. As National Defense warned in its cover story this month, "Quiet diesel submarines are emerging as the ultimate stealth weapon."

These subs can be much smaller than big American or Russian nuclear subs. So they are consequently much harder to detect. The latest diesel-electric drives also are very quiet, and muffling sound is the key stealth weapon in undersea warfare.

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