After the Iranian Navy warned that it had deployed its North Korean-made light attack submarines for operations in the Strait of Hormuz, most notably the "Ghadir" class, which is manufactured under license based on Korean designs and technology, questions were raised about the ships' ability to threaten valuable US Navy assets at sea.
Data from simulated battles with such diesel-electric machines reveals that small submarines often manage to surprise US defenses through specific tactics of camouflage on the seabed, reports Military Watch Magazine.
Due to the high frequency of exercises between the Royal Australian Navy and the Royal Australian Navy, The US, Australian Collins-class diesel-electric attack submarines have been particularly frequently tested against US warships and were reported during the RIMPAC 2000 exercises to have sunk two US nuclear submarines and to have come dangerously close to the USS Abraham Lincoln (the world's largest aircraft carrier). Although the exercises were planned and the US carrier strike group knew the Australian ship was in the designated target area, they had not yet been able to locate it.
Subsequently, in 2001, during Operation Tandem Thrust, analyst Derek Woolner reported that a Collins-class submarine sank "two US amphibious assault ships in waters between 70 and 80 metres deep, slightly more than the length of the submarine itself". In October 2002, Collins-class submarines "chased and killed" the US nuclear submarine USS Olympia during exercises near Hawaii. The Australian submarine's commander noted that the larger US ship's greater speed and acceleration were not an advantage because "it just means you make more noise when you go faster." In 2003, Collins-class ships were reported to have destroyed two US Navy nuclear submarines and an aircraft carrier during simulated engagements. The US Navy's decades-long combat history against diesel-electric submarines suggests that the ships supplied to Iran by North Korea could pose a very serious threat to US aircraft carriers, including amphibious assault ships, nuclear attack submarines, and aircraft carriers.