The U.S. Navy is rethinking how it will use its submarines in a future Pacific War. The problem is that a campaign against Chinese shipping is unlikely, in part because of what actually happened during the last great anti-shipping campaign, which occurred during World War II (1939-45). After the war, the U.S. analyzed its operations against Japanese shipping and found that submarines were important but not the only weapon effective against shipping. Some 8.9 million tons of Japanese shipping was sunk or so seriously damaged (disabled) at the end of the war. Submarines accounted for 54.7 percent of this. But 16.3 percent was attributable to carrier-based aircraft, 14.5 percent to land- based planes, and 9.3 percent to mines (most dropped by B-29s). Less than one percent was due to surface gunfire and the balance of 4 percent was caused by accidents.
Because of their ability to operate in enemy-controlled (mainly by land-based aircraft) waters, submarines accounted for about 60 percent of the damage until the final months of the war. Then, during late 1944, carrier task forces went deep into enemy controlled areas, defending themselves against land-based warplanes and sinking a large numbers of ships. After April, 1945, Japanese shipping was restricted to the Korean and Manchurian runs and to shallow coastal waters. At this point the naval mines dropped by B-29s in Japanese harbors and inland waterways accounted for 50 percent of all ships sunk or damaged. That was then, but sixty years later the United States is able to monitor large ocean areas and has aircraft that are able to hit anything that's spotted.
Meanwhile, the U.S. has adopted a new approach to any potential war with China. The U.S. Department of Defense has been told that, for the foreseeable future, there will be no more large-scale land campaigns. The air force, navy, and marines responded with a plan (AirSea Battle) that has been in the work for years. The new strategy is designed to cope with the rising power of China in the Pacific. AirSea Battle involves tighter planning and coordination of navy, marine, and navy forces, plus the development of some new weapons and tactics and cooperation with allies.
AirSea Battle has been widely accepted, as China continues to make all its neighbors nervous. That's because the Chinese name for China translates as "middle kingdom" as in "China is the middle of the world." The Chinese government, a communist dictatorship by any other name, is using nationalism to keep its pro-democracy opposition off balance. China has border disputes, expressed or implied, with all its neighbors. This has made the neighbors uneasy, especially as Chinese military forces have been modernized and more aggressive over the last decade.
While Air-Sea Battle was developed to keep the United States out of extensive land combat (the navy still has commandos and marines for brief operations ashore), those kinds of wars tend to show up when you least expect, want, or are prepared for them. For the moment, U.S. military planners believe they can avoid a large land war.
The U.S. Navy has been studying (and wargaming) the situation, and that included an examination of American submarine use since World War II. After the 1960s, the U.S. shifted to using only nuclear propelled submarines. During the Cold War (1948-91) American subs were meant for use in defeating the growing Soviet (Russian) fleet. That force disappeared in the 1990s. At that point the Chinese fleet got larger and modernized but is still nowhere near the size of the Soviet Navy. But this time the U.S. was facing a major trading nation. Unlike Russia, which was largely self-sufficient (or could get what it needed overland from neighbors), China requires thousands of ships a year to handle exports and imports. Like Japan during World War II, China is vulnerable here.
AirSea battle concentrates on military operations. But these will be heavily influenced by economic factors. For example, during World War II the United States was a largely self-sufficient "continental power." We exported much (more than any other nation on the planet), but did not have to import much. That has changed. Now the U.S. has to import a lot of its oil, special raw materials (like "rare earths" from China), and a lot of manufactured goods. The U.S. is now like much of the rest of the world, China included. If there were a maritime blockade of China, the U.S. and many other Chinese trading partners would suffer severe economic disruptions. There would be massive unemployment for all concerned and that would happen despite energetic efforts by everyone to find alternative sources to goods no longer available because of the disruption of the China trade.
Then there is the risk of nuclear war. Since the first nuclear weapons were used in 1945, there has been the longest period of peace between major powers in human history. These days a "major power" is one that has nuclear weapons and can deliver them against other nuclear armed nations. Thus any maritime blockade of China will be a very risky undertaking. That said, it can be done without submarines. Simply order the Western maritime insurance companies to withdraw insurance for ships or cargoes entering or leaving China. That will have immediate effect. China can scramble to try and replace the insurance covering, but along with the "insurance bomb" comes the U.S. declaration that the coastal waters of China are now under blockade and any ship ignoring that is subject to attack. It goes downhill from there, until compromise and moderation replace the war fever.
Meanwhile, the nuclear submarine community has done the math and found that their greatest contribution these days is not attacking enemy warships but land bombardment with cruise missiles and intelligence collecting. Since the first nuclear subs showed up in the 1950s, only one, a British boat, has used a torpedo to sink a hostile warship. But hundreds of cruise missiles have been launched at land targets and uncounted (because they are highly classified) intelligence missions have been, and continue to be, carried out. All that is the recent past for subs and is likely to be the future as well. World War II in the Pacific is not likely to be rerun. The U.S. Navy still expects its subs to go after enemy warships and its surface and air forces to battle enemy subs. But a major war on shipping is much less likely.