Stratfor is kicking off a geopolitical analysis of the Yangtze river, which they dumb the Mississippi of China. Like the Mississippi, the Yangtze river is of prime economic importance to the Chinese economically and politically. In periods when the Han people were not unified the dividing line was often the Yangtze river, separating the northern kingdoms from the southern kingdoms. Here is a video below.
Here is an image showing both the Yangtze and the Yellow rivers, and as you can see, some of the most important economic city centers in China, Shanghai on the cost and Chongqing in the interior, lie on the Yangtze river.
Unlike the Mississippi however, where there are no man made damns obstructing sail able traffic, you can sale from Minneapolis all the way to the Gulf of Mexico, the Yangtze has the three Gorges Dam, currently the largest in the world. The Chinese have built ship lifts and a series of locks to ensure that river traffic can continue, but it does pose an exploitable weakness. This is tempered by the fact that the three gorges damn is over a thousand kilometers away from the coasts.
Individuals, who have read my post on the economic and geopolitical importance of the Mississippi, will instantly know that keeping this river way open to the world is of paramount importance. This also illustrates why the Chinese are acting the way they are in the South China sea. While the islands possess some importance due to international treaties concerning exclusive economic zones, the real importance.
Looking at a map of East Asia you will see that China only has one coast, whereas the US has three, and that their access to open water is extremely hampered. The US faced the same situation concerning their gulf coast and the Mississippi river and the access way of its good to the world, which explains the Monroe Doctrine, and the risk that the fledgling US faced is even greater for the Chinese. In the event of a potential blockade there are only four openings outside of the East China and South China Sea; I do not inlcude the Sea of Japan and the access way to the North Pacific for obvious reasons.
From Japan, a US ally, to Taiwan, another US ally, there are the Ryuku islands that would strongly favor the US in the event of hostilities as they add additional land based systems that could take part of a naval blockade in that region. There is a relatively large opening between Taiwan and the Philippines, but the Philippines has been moving ever closer to the US, and there is a second string of islands, the Bonjin and a series of islands to the south of the tropic of cancer, that the US could potentially utilize.
The openings to the South China sea are even more problematic as the Sulu Sea, the Java Sea, and the the Andoman Sea are very small and present great opportunities for a major naval power to enforce a blockade without exerting tremendous amounts of resources. Another item of note is that the Straits of Malaca, where 90% of all China's oil and a large portion of their exports to Europe sail. Cutting off the straights of Malaca would be disastrous for the Chinese. The ultimate problem being, that given various islands could serve as useful points from which the US could fight a naval war, the Chinese are at an extreme disadvantage.
True, many naval stations, such as in Singapore and the Philippines are no longer in use by the United States, the fact is that this could change and the US is already making overtures for greater military cooperation between itself and the south east island nations. The greatest fear China has would be to send out their fledgling navy against, not only the US navy or allied navies, but also the available anti-ship land defenses that could be used so effectively in the region. This is also why China is developing their own robust anti-ship defense systems since a bottleneck for them is also a bottleneck for their enemy.
Ultimately this about the potential threat the US posses to China, any large naval power could use these features against China, but only the US right now possess a such a naval power that makes them a legitimate threat in this way if hostility ever broke out. China is all too aware of this uncomfortable reality, and this explains their actions in concerning the disputed islands and their efforts to modernize their navy and develop a robust land based naval defense system.