Because the Party's scientific theory and correct line, principles and policies are the scientific guidelines for China's national defense security. In the new century and new stage, many profound changes have taken place in China's security environment. Peace and development are still the theme of the times, but the world is not peaceful, hegemonism and power politics have shown new manifestations, ethnic and religious contradictions and conflicts are complicated, traditional and non-traditional security threats are intertwined, the harm of terrorism is rising, the situation in the Taiwan Strait is becoming increasingly severe, and hostile forces at home and abroad are stepping up sabotage activities. We also have some prominent contradictions and problems in the construction of national defense security. The situation and tasks urgently require us to always put national sovereignty and security in the first place and strive to do a good job in safeguarding national defense security. Maintaining national defense security requires that the ruling party must proceed from the international environment and national conditions, put forward correct theories and policies, and effectively guide national defense construction. Since the founding of New China, no matter how the international situation changes and the domestic situation develops, our party has always given top priority to safeguarding national sovereignty and security, constantly made theoretical innovations, formulated and implemented a series of correct lines, principles and policies, and effectively safeguarded national defense security while realizing economic and social development. At present, we are in the background of world multipolarization, economic globalization and rapid development of science and technology, and in the environment of reform, opening up and socialist market economy. It is very important and urgent to build a strong and consolidated national defense and safeguard the expanding national interests, and it is also more complicated and arduous. Whether this major strategic task can be completed is the most practical test of the party's advanced nature. The new situation and tasks require our Party to adhere to the guidance of Mao Zedong Thought, Deng Xiaoping Theory and Theory of Three Represents, accurately grasp the new challenges brought by the development and changes at home and abroad to China's national defense security, proceed from the fundamental interests of the overwhelming majority of the people, consciously conform to the development trend of the times and the requirements of national development and progress, scientifically understand and define national interests, establish reasonable national defense security objectives, and formulate correct national security strategies and military strategies, as well as a series of principles and policies corresponding to this. Only in this way can the party give scientific guidance to the practice of national defense security and firmly grasp the correct direction of national defense security, so as to ensure national defense security to the maximum extent and safeguard national interests.