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Jun 26, 2012 | 10:30 GMT

6 mins read

U.S., China: Exploring the Undersea Balance

U.S., China: Exploring the Undersea Balance

Editor's note: Rim of the Pacific (RIMPAC), a multinational maritime exercise conducted every two years around the Hawaiian Islands, will be held June 27-Aug. 7. This year's exercises mark an important step in the projection of power and interoperability between participating nations as the United States begins its strategic shift toward the Pacific region, particularly with regard to China, the region's rising power, which was not among the 21 nations invited by Washington to participate. This series will analyze the naval capabilities displayed during the exercises and weigh them in the context of regional relationships.

Of the 22 nations participating in this year's RIMPAC maritime exercises, four will contribute submarines, and the United States will be the only one to contribute nuclear-powered submarines. China will likely be interested in the U.S. submarine capability on display during RIMPAC. Over the past two decades, China's submarine fleet has grown significantly in size and capability. The fleet plays an important role in the immediate defense of Chinese territorial waters and in China's "counterintervention" doctrine. However, despite China's considerable progress in developing undersea capabilities, in an unlikely conflict with the United States, China's submarine operations would remain constrained by geographic factors and the superior capabilities of the U.S. submarine fleet.

The 1990s were a major turning point for the Chinese submarine fleet. China built or purchased several new designs, setting the stage for a significant expansion in the number of operational boats and heralding a substantial improvement in quality from the Romeo- and Ming-class designs it previously operated. In 1994, the Chinese commissioned their first Kilo-class submarine — bought from Russia — and launched the first indigenous Song-class submarine (although this vessel did not enter full operational service until 1999). In 1995 or 1996, China also began constructing its new nuclear attack Shang-class submarine.

China's Capabilities

The investments the Chinese have made in their submarine fleet have paid off: The Chinese navy now operates the largest conventional-powered submarine fleet in the world, along with a small but growing nuclear-powered submarine fleet. Currently, the Chinese are believed to be working on an improved Yuan-class diesel-electric submarine that likely can use air independent propulsion, which would allow the vessel to remain submerged for longer periods of time.

The Chinese diesel-electric-powered submarines can be useful in several different operational scenarios. These can range from attacking enemy vessels to conducting mine-laying operations and even reconnaissance missions. Most important, Chinese submarines are one of the primary tools in Beijing's efforts to build up a counterintervention capability based on denying or limiting the access of U.S. (and allied) vessels to the Chinese "near seas." From Beijing's point of view, these include the Yellow, East China and South China seas.

Submarines in particular are the most survivable Chinese naval platform. They can, at least in theory, interdict enemy vessels before they even approach the Chinese near seas by conducting operations in the larger sea space between what China calls the first and second island chains (roughly speaking, the Philippine Sea).

The U.S. Department of Defense calls China's counterintervention strategy "anti-access/area denial" (A2/AD). Numerous platforms, weapons and tactics are part of this strategy, including a much talked about anti-ship ballistic missile. However, the former head of U.S. Pacific Command Adm. Robert Willard noted in December 2010 that the Chinese submarine fleet remains the primary threat in the A2/AD arsenal. This potential threat is highlighted by an incident that occurred in October 2006, when a Chinese Song-class boat remained undetected until it surfaced less than eight kilometers (five miles) away from a U.S. carrier — a distance well within the range of the Chinese submarine's torpedoes and anti-ship missiles.

Chinese conventional submarines, though lacking in endurance and size when compared with ocean-going nuclear-powered submarines, are better suited to the littoral waters of the near seas. Stealthy diesel-electric boats operating at low speed can remain better hidden in the littoral waters because in shallow water, acoustic energy from passive and active sonar propagation is more prone to reflect off the seabed than in deep water. However, when operating in blue-water conditions, submarine tonals propagate much farther and therefore submarines are significantly more vulnerable to detection. When operating in the littoral waters of the near seas, the Chinese submarines will also have the advantage of air cover that can chase away enemy sub-hunting planes such as the P-3 Orion.

The U.S. Submarine Fleet

Though Washington remains concerned about the growing capabilities of Beijing's submarine fleet, it also understands that the United States' own silent service remains, by far, the most advanced and effective force in the world. With deployments around the world and with the need for an ocean-going fleet capable of securing far-flung sea lanes and trade routes, the United States' active fleet does not include any diesel-electric submarines. Instead, the United States maintains the largest fleet of long-endurance nuclear attack submarines in the world (which, at 54 boats, is about the same size as the Chinese conventional submarine fleet). However, U.S. submarines are dispersed around the world in support of the United States' global interests.

Since the height of the Cold War when the United States was deeply concerned about a third Battle of the Atlantic against Soviet submarines, the United States has made impressive strides in harnessing technologies related to both passive acoustic detection and submarine silencing. These advances have made the nuclear submarine the pre-eminent anti-submarine weapon in the U.S. arsenal. The disparity is especially prominent when comparing U.S. nuclear submarines such as the Virginia- or Seawolf-classes to the comparatively very noisy Chinese Shang-class nuclear submarine.

Moreover, Chinese conventional submarine operations will be at a greater disadvantage than U.S. undersea forces when operating in deep water environments, particularly the Philippine Sea. Not only would the Chinese submarines be operating beyond much of the Chinese air cover, but they would also find it challenging just to get there. The main exits from the Chinese near seas into the Philippine Sea are through the Ryukyu Islands northeast of Taiwan or the Luzon strait southeast of Taiwan. These exits are strategic bottlenecks that could be covered by U.S. nuclear submarines conducting anti-submarine warfare patrols and by ocean surveillance systems utilizing passive acoustic detection.

The Chinese submarine fleet has grown significantly in size and capability and remains a key component of China's A2/AD strategy. However, in the unlikely event that the Chinese face off against the United States in an armed conflict, the Chinese submarine fleet would be constrained by considerable geographic challenges and would be going up against a far more robust U.S. submarine fleet.

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