Chinese behavior in the South China Sea is viewed by many as implacably aggressive. China contends it is consistently defensive and even pacifistic. To cut through the rhetoric we can look at the combination of geography and history in the past 150 years to explain Chinese behavior. As Stratfor has noted, China has core geographic imperatives. Western powers (and Japan after adopting Western weapons and attitudes) penetrated these core territories during a long period of weakness that lasted from about 1840 to 1950. As a result, since 1950 Chinese leaders have fought offensive and often preemptive wars with each one of their neighbors, but they’ve been able to claim these are defensive measures. A careful look at the history suggests there is some merit to Chinese positions, but most often they are used as rhetoric to justify aggression.
The geographic regions of most concern to China consist of its core Han territories between the Yellow and Yangtze rivers, its tributary states such as the Muslim Republics in the West, and the littorals and oceanic avenues of approach to Chinese territory. Hereafter they will simply be referred to as key territories. For much of Chinese history these territories have been the route of invaders ranging from Mongolian invaders from the North West in the 13th century to the wokou (literally translated as dwarf pirates) along the South Eastern coast in the 16th. Chinese diplomacy was also predicated on their being the center of diplomacy, after all, they are the Middle Kingdom, with many tributaries and neighboring nations acting as figurative sons or brothers to their Chinese father. For example, Hideyoshi’s 1592 invasion of Korea was explicitly announced as a prelude to assaulting China and changing the East Asian world order. My forthcoming book, Decisive Battles in Chinese History, describes what happened to China when those key regions were penetrated starting with the Opium War (1839-1842). British warships with shallow drafts often bypassed key positions and easily out fought the apathetic ethnic Han troops who did not wish to fight on the behalf of the foreign rulers of the Manchu Dynasty. The resulting treaty overturned the nature of Chinese diplomacy, forcibly opened many Chinese cities and penetrated on of their key geographic areas.Chinese victories for the next half century after the Opium War showed evidence of their adaptability, inherent strength, and desire to defend their territories. Chinese armies armed with Western-style rifles and diplomatic tactics recovered and even expanded further into central Asia. They fought a brief war and resolved the conflict with Russia over the pivotal Ili valley and province. They subdued the Taiping rebellion that engulfed most of China during roughly the same period as the American Civil War, and defeated Muslim-led revolts in the remote Southwest of Chinese territory. This period proved that an active and capable leader could still secure and recover territory, as well as make modest improvements in adopting Western arms in the face of resistance from traditionalists and cultural elites. Compared to the collapse of the Song and Ming dynasties (in the 12th and 17th centuries respectively), the Qing government performed well against stronger threats in creating peace and prosperity.
With the exception of trade cities opened by the British in key Chinese territory, the Chinese were able to respond to land-based threats and internal rebellions in their core territories and their tributary states, but the European naval threats to areas that were nominally under their control were a different story. The Chinese fought and lost two wars against the British, which prompted military reforms and they lost two more pivotal wars in the latter decades of the century that showed their efforts at modernizing were stumbling and inadequate. The first of these was against the French in 1883-1885 for control of territory we now know as Vietnam, and which was a frequent tributary in China’s long history and hence one of their key territories. The failures of this war were stark, but not complete. They mostly revealed that the efforts at military reform were led by various local leaders in an inconsistent fashion hampered by factional politics. The uneven reform resulted in modern ships and armies that lacked standardized equipment, spare parts, common training, and adequate leadership. This was a common theme until the end of World War II, as China at various points in this period obtained Soviet, German, Japanese, American, German, British, and French advisers and equipment.
Assuming they did have working equipment, good doctrine and rigorous training they faced factional infighting between various governors and regional leaders. Once the conflict with France began for example, the key reform leader Li Hongzhang, a skilled veteran of the Taiping and Muslim rebellions, would not allow his Northern Chinese fleet to move south. He jealously procured and guarded the very best ships (ironically French built), not wanting to risk them. Unlike the Opium War though, the Chinese performance was not such a clear cut failure. China scored several clear victories over French infantry in Northern Vietnam, and only lost control of a small amount of territory on the periphery that became the French colony of Vietnam.
It was the second of these two conflicts, the Japanese war in 1894-1895, however, that clearly revealed Chinese weakness and signaled an era of Western (and Japanese) predations. The conduct of China’s army and sea forces were a complete embarrassment for the Qing Dynasty and their Manchu rulers. The Chinese army was sent retreating , core Chinese territory was penetrated, and Beijing was close to falling. Despite having superior numbers, the navy was completely destroyed. Once again, the Northern and Southern Chinese navies failed to assist each other, but even if they had acted in a concerted effort it likely would not have helped. The Japanese fleet completely out maneuvered, outperformed, and annihilated the much larger Chinese fleet. The resulting treaty removed Korea and Taiwan from Chinese orbit and a key tributary and part of traditional China respectively, and subjected China to years of Japanese aggression. Many local Japanese leaders regularly seized territory long considered by Chinese rulers as vital to the defense of the capital and cultural cradle of their civilization. The last of the puppet states in Manchuria would eventually lead to the start of World War II.After the Sino Japanese War of 1894-1895, Germany, Russia, and Great Britain demanded additional trade concessions in ports, the rights to use railroads, and special protections for missionaries. American concessions were smaller, but still consisted of the Open Door policy that allowed American goods to flood China. In short, the Sino Japanese War revealed the impotence of the Manchus in the face of aggression from Japan. Western nations soon competed to see who could take the most advantage of China’s vulnerable state. Geographically, these defeats centered on the three geographic territories listed above: core Chinese territory, traditional tributary states like Vietnam and Korea, and approaches from the sea near the ports seized.
It wasn’t until 1949 that China was unified, and it is no surprise that their primary concern since that time has been to secure their core territories, protect bordering states that were historically tributary clients, readjust their borders in favor of Chinese interest, and to aggressively protect its seaward approaches. In 1950, when many analysts believed China needed years of recovery, Mao launched an attack on American forces in Korea nearing the Chinese border. A few years later they seized several islands controlled by Taiwan and Mao signaled his intention to take the rest of their territory. Only the timely intervention of American forces prevented that action. Chinese wanted to address the unequal treaties regarding Indian territory in 1962 and Outer Mongolian territory in the Ussuri River Skirmish with Soviet Union (1969). After a war with Vietnam in 1979, China had settled its control over core territories (except Taiwan) and states that were former tributes. The final key remains the approaches to China which leads to today’s flashpoints in the South and East China Sea where China is placing military facilities, landing strips, and various missile batteries on contested islands,or building islands on which to place these capabilities.
When placed in this historical context Chinese behavior is and goals are easier to understand. The seizure of territory in all three of the traditional areas, adjusting borders and the removal of foreign troops from those territories, such as the Americans in Korea or Soviets in Vietnam, all can be seen as action which sought to protect China’s core. Yet the Chinese were not forced into preemptive wars with almost every one of their neighbors. The traditional narrative of a China that is set upon by greedy Westerners leaves out important details that suggest China’s offensives were optional. It is true that MacArthur was approaching the Yalu River bordering Chinese territory, but the Chinese had strong defensive positions against a potential enemy that was at the end of its logistical limits and an avowed goal to stop at the Yalu river when China launched their attack in the Korean war. There was no immediate threat to Chinese territory and China was still recovering from its long internal civil war. The territory they seized from India was a rather small, and the Indians already had their own share of South Asian problems. The Chinese could have used diplomacy with both India and Pakistan to leverage what they wanted without a preemptive strike. At the time of Ussuri River Skirmish, China was nominally an ally of the Soviet Union, and had a 1950 treaty of friendship that recognized the pivotal nature of Mongolian territory to Chinese security.
Understanding this behavior will allow the United States to properly adopt foreign policy positions that will perhaps convince China there is no need to aggressively defend those traditionally key territories because the current measures are sufficient. For example, freedom of the seas operations reaffirm the import of international law and make it less likely that matters will be settled by force.
If a conflict occurs United States has and can take even more appropriate measures to prevent conflict. China’s much vaunted Anti Access/Area Denial (A2/AD) strategy is frequently discussed but not as formidable as many think. Carrier-killing and hyper sonic missiles do have impressive speeds and capabilities but they are also simply the newest version of technology that have been around for 70 years. Over that time the United States developed robust defenses against this threat. To begin with for example they can use the combat air patrol and repurposed Ohio class submarines to knock out launch sites. The latter is particularly deadly as they can carry and launch more land attack missiles than an entire carrier group combined, launch them from a stealth platform, and fire all of those missiles within six minutes. The navy is using the new F-35 to network with older fighters to extend their range beyond the horizon. The next layer of defense are Aegis destroyers, and they are being networked with the F-35 and their radar is receiving improvements that make them 35 times stronger. The rapid capabilities office wants to re-purpose howitzers to target and destroy incoming missiles. (Though placing offensive weapons near contested islands will hardly relax tensions.)
Given the current climate in the region it's tough to believe a simple knowledge of history will ease all of the tension but the United States can understand how to react and respond in the region without aggravating historic concerns and be more likely to see through Chinese masking rhetoric. They have a reason to be cautious about Chinese capabilities and objectives, but they have the tactics and weapons systems to counter the Chinese threat.
 This also related to the Chinese concept of Imperial Confucianism, which ordered society based on the duties that one had to take based on their relationship. A ruler had to be a good representative of Heaven, a father a good father, a son a good son and so forth. Chinese rulers and court officials incorporated their foreign relations into the same ideas.
 Richard Horowitz, “Beyond the Marble Boat: The transformation of the Chinese military from 1850-1911,” in A Military History of China, David Graf, Robin Higham ed. (New York: Westview Press, 2002)153-174. Also see chapters 5 and 6 of Bruce Elleman, Modern Chinese Warfare- 1795-1989. New York: Routledge Press, 2001.
 For a representative example you might examine the equipment and performance of the Chinese army during the Battle of Shanghai. Harmsen, Peter. Shanghai: 1937 Stalingrad on the Yangtze. (New York: Casemate, 2015).
 See this for Chinese motivations in their war with Vietnam. Xiaoming Zhang, Deng Xiaoping's Long War The Military Conflict between China and Vietnam, 1979-1991 ( New York: UNC Press, 2016).
 The Ohio class submarine can carry as many as 154 land attack missiles. The other ships in a carrier group have multiple functions, and hence carry a smaller amount of different kinds of missiles.