The Chinese have an estimated 55 diesel-electric submarines in service, including several modern, Russian-built Kilo-class units. In addition, China is building advanced conventional as well as nuclear-propelled torpedo attack submarines. (The U.S. Navy now operates only nuclear-propelled attack submarines -- 55 SSNs are in commission.)

Non-nuclear submarines are difficult to locate -- if operated by competent crews -- especially in coastal or littoral waters. In those areas the advanced submarine detection systems developed by the U.S. and other NATO navies during the Cold War have limited effectiveness because of shallow depths and the massive noise put into the water by coastal shipping, fishing craft, offshore oil drilling rigs, and other sources.

However, China's conventional submarines, like their nuclear-propelled units, spend little time at sea. Researcher Hans M. Kristensen, writing for the Federation of American Scientists, reports that China's "55 general-purpose submarines conducted  a total of six patrols during 2007, slightly better than the two patrols conducted in 2006 and zero in 2005."

The patrol information was obtained from the U.S. Navy.  Kristensen continued, "Just what constitutes a Chinese 'patrol' is secret, according to the U.S. Navy…."

This writer has learned that such patrols have a maximum of about 30 days with the boats averaging a speed of four or five knots while on patrol. Still, these patrols have demonstrated that the submarines can locate U.S. ships, as evidenced by the surprise of U.S. officials when the carrier Kitty Hawk (CV 63) encountered a Song-class diesel submarine. Obviously, diesel boats cannot effectively track U.S. warships, but could probably be guided to such intercepts by reconnaissance aircraft or satellites.

Little is known about the operations of China's nuclear torpedo-attack submarines (SSN). However, according to reliable sources, neither the first Chinese ballistic missile submarine (SSBN) of the Xia design, launched 25 years ago, nor the new Jin-class SSBNs launched since 2004 have undertaken a patrol. Indeed, reportedly the Chinese still do not have an operational submarine-launched ballistic missile for those craft.

Rather, it is the non-nuclear submarines that should be of major concern to U.S. and allied naval planners who wish to operate in Far Eastern waters.