As an organic aggregate, the country condenses into a unity according to its beliefs, spirit and morality, which makes it have life function, occupy a certain space, grow, shrink and decline under certain conditions. A country's sovereign space and interest space often match its resources, energy, population and development level. The boundary of any country is not static, but constantly rolling, becoming a "dynamic boundary". This change is not only consistent with theoretical inference, but also with the evolutionary history of human history. In an immature historical process, a country should not only hold an idealistic vision for the future of mankind, but also pursue the maximization of national interests under the existing conditions, which is a normal and helpless historical choice for any country. After the collapse of the bipolar confrontation pattern, the unipolar order began to take shape, and the power rule and conceited moral and value mission operation of the United States were still subject to multipolar soft confrontation from time to time. Although the multipolar and unipolar struggle is still full of uncertainty, this possible alternative force and pattern is still a positive message, because the world will become more democratic, balanced and just. But it is still unsatisfactory, because the world is still controlled and dominated by several big countries, the world is still in contradictions and risks, the zero-sum game is far from being completely eliminated, the competitive relationship model has not been broken, and the overall interests of mankind are greatly threatened and challenged. Although today's world has entered the era of globalization and economic dependence has increased, both China and Japan are striving for the maximization of national interests and promoting the strong extension of interest space. The national essence and human development model that cannot be separated from political Darwinian rules still dominate the realistic choice and future direction of China and Japan. Only from this height can we examine the past, present and future of China and Japan. Sino-Japanese relations will be more sober and rational. As a big country in the Asia-Pacific region and the second largest economy in the world, the core content of Japan's national strategy has remained unchanged: achieving complete national independence and territorial integrity; Maintain the sustainable development and leading position of the economy; Have a huge arsenal of unconventional weapons, including nuclear weapons; Have the international legal status and freedom of international action of a normal country; Strive for WTO entry and enhance Japan's political status; Promote western democratic values and political systems; Advocate the establishment of a unipolar world. All these serve the main goal of Japan's dream of becoming a rich country. The contents of China's national strategy are: promoting modernization; To maintain the existing ideology and political model, we should not only prevent the return of traditional culture, but also prevent the subversion of western values; Safeguarding national unity and territorial integrity; Establish a multipolar world; Create a stable and favorable national environment, promote world prosperity, peace and world harmony, and realize national rejuvenation as soon as possible. With the development of the international situation, China abandoned the ideological diplomatic line, and pragmatism occupied the dominant position, so it was no longer included in the main national goal. Surrounding geopolitics, historical grievances, the rise of the United States, especially the strong presence of the United States, have made the relationship between China and Japan, which is in trouble because of the intersection of strategic content and goals, worse, and contradictions and oppositions have arisen one after another. The main reason is that the Japanese can't tolerate the rise of China and once again occupy a comparative advantage. There are many reasons and explanations for China's revival trend, Japan's new trend towards a "normalized" country and the tension between the two countries. Today, the introduction of a famous "wooden barrel" theory embedded in the field of international relations may better solve the current predicament. The so-called wooden barrel theory, that is, a wooden barrel is composed of many boards of different lengths, and its water holding capacity is not determined by the average length of the longest board or all boards, but by the shortest board. In order to improve the overall effect of the barrel, we should not increase the length of the longest board, but make great efforts to fill the length of the shortest board. Looking back at China and Japan, after World War II, Japan experienced the golden age of capitalist development, and its economic aggregate jumped to the second place in the world, becoming the second largest economy in the world after the United States. At that time, due to well-known historical reasons, China was far behind Japanese in economy. However, since the reform and opening up, China's economy has developed rapidly, and its economic strength ranks fourth in the world according to GDP. Considering geopolitics, taking the United States as a reference and summarizing the huge empire of human society, China and Japan do not have the conditions to become powerful countries. As far as China is concerned, its disadvantages are mainly concentrated in the fields of economy, science and technology, especially basic research and original innovation, social organization and system, and cultural attraction, while its advantages are mainly concentrated in political and military strength. However, Japan's disadvantages are concentrated in politics, its political and military forces are restricted by the "Peace Constitution", its resources and energy imports are insufficient, and its advantages are concentrated in economy and technology, especially manufacturing technology and high-quality population. If the "wooden barrel" theory is introduced into international relations and geopolitics, it can be expressed as follows: if the factors that determine a country's national strength are different in intensity and size, then the key factor that determines the country's comprehensive national strength will depend on one or several weakest factors and will be mainly subject to bottleneck factors. However, in recent years, great changes have just taken place in the weak areas of their respective countries, which will attract more attention and vigilance than maintaining a leading position in the advantageous areas of their respective countries, because these changes can quickly and actively enhance the international status and comprehensive national strength of the two countries and break through the bottleneck, so this situation has aggravated the alert situation caused by historical sovereignty and interests and the contraction and expansion of the US-Japan alliance to a certain extent. Supplement: As for the future direction of Japan, some people think that Japan will break through the peaceful constitution and return to the path of militarism, which will lead to continued tension in East Asia. However, there is no need to exaggerate Japan's development. In fact, as a country ruled by law, Japan's constitution is the country's fundamental law and the highest regulation. To modify it, strict procedures and conditions are needed. The Constitution stipulates: "The revision of this Constitution must be approved by more than two thirds of all the members of the two houses, initiated by the National Assembly, proposed to the people, and recognized by the people. This recognition must be voted in a special national vote or an election stipulated by the National Assembly, and it must be agreed by more than half. " Therefore, it is not easy to amend the constitution. At the same time, most of Japan's elites and nationals are still in favor of the theory of industrial trade and the theory of Chinese studies, and most people are still opposed to war. Japan's post-war development path also shows that it has chosen new means to gain benefits through politics, economy and trade to a certain extent. In addition, Japan's serious lack of resources and energy will greatly limit its strategic intentions. I'm afraid Japan is willing but unable to do so. China and Japan belong to the sub-cultural circle, separated only by a strip of water, and their geographical positions are very close. There are frequent cultural exchanges in ancient times, which have a certain degree of * * *. On the other hand, China and Japan are the same species of literature, but due to the cultural differences between China and Japan. Japan has studied westernization, including western natural science and social science, and this trend has not changed until now. In fact, Japanese culture has undergone a primitive transformation, which is different from China culture and western culture. There are still great differences between the two countries in history, culture and value orientation. Compared with the contradictions in external and explicit fields such as energy, military affairs, territory and WTO entry, the gap between the two sides in history, concepts, ways of thinking and national character is more acute and difficult to reconcile in the short term. Although the grim situation of Sino-Japanese relations has not reached a dead end in history, the improvement of Sino-Japanese relations still needs great efforts. In particular, the emotional environment of the two countries has greatly reduced the retreat space of the two countries and limited the realistic choices of the two governments. However, as long as China and Japan are patient, calm and lively, not bound by domestic narrow nationalism, and have no intention to show their strength and carry out domestic reforms thoroughly, it is still possible for them to enter the realm of rationality, maturity, stability and harmony.