When the international system is considered, it is seen that the priority of states is to ensure their own security. In particular, the realist theory is a theory that tries to understand how states acting based on their national interests and how to obtain its security in the international system without a superior authority.
Realism tries to explain which security strategy states should choose in order to provide the most important targets of the states’s survival. From this point of view, there are two basic security strategies to ensure security; competitive strategy and cooperative strategy. In order to ensure security, the competitive theory involves acquiring more weapons, participating in the alliance and the use of military force when necessary. On the other hand, considering the cooperative strategy, it claims that security can be improved through more cooperations and mutual relations.
On the basis of both approaches, there is the idea of ensuring the state’s survival. In the context of Realism, even if it is seen that there is a need to achieve power in different ways according to both approaches in terms of ensuring survival, this theory tries to explain a system in which both arms race and the agreement to control armament.
Separation of Realism Within Itself
Although they have important similarities, it is necessary to distinguish between its members in order to fully understand the realist theory. Because these theories, which are considered sub-theories of realist theory, may have differences in some important issues. In this context, the most fundamental distinction within the Realism family is the line that emphasizes the impact of the international system (Structural Realism) and the line that stresses the motivation and basic aims of states (Motivational Realism). This separation is generally called the differentiation of the motivation of the international structure-states.
Waltz’s Structural Realism
Waltz claim that the structure of the international system forces states to compete and that it is difficult to get rid of this competitive environment. In general, it is known that blocking competition is difficult in a system without a superior authority. Because states can not be sure of each other’s actions, even a security movement by one state can pose a security problem for the other state.
In Neo-Realism, states apply balancing techniques to ensure their security in anarchic system. But despite balancing, it is still very difficult to prevent war because every power wants to be hegemon power in an anarchical international system.
According to Waltz, states have two options to defend themselves. Internal balancing and external balancing. When we look at the internal balance, it basically means that the state increases its economic capacity and by that opposes the aggressor state. In a sense, this means self-help of state. It is possible to provide survival of state by combining two elements. They are to increase their power and take into account the power of prospective rival states.
The second option is external balance. In other words, to forge an alliance with other states to defend itself. In general, because there is no external balancing in the bipolar system, there is only internal balancing, but from today’s point of view, states prefer external balancing. Because in a multipolar system, states need alliances to maintain their existence and ensure their security.
In addition, bandwagoning is also an important balancing strategy, which is an alternative to external balancing. Because states are siding with weak ones to balance powerful ones in balancing while pursuing states compete to gain more income by participating in the power. The best examples of these options are Operation Desert Storm, which took place in 1991 under the name of the operation to rescue Kuwait from Iraq. There was England on the base of the operation. Britain was essentially pursuing the United States and aimed at benefiting from Kuwait’s oil. Another example is the operation against Libya in 2011. Western states have attacked a state that is experiencing civil war like Libya as a coalition. Under the name of operation NATO, weak states have pursued (bandwagoning) France, leading them to play a role in the table after the war.
According to the Scheweller, the greedy state, can make different choices than the security seeker state, and these states tend to pursue bandwagoning strategy because they intend to gain power. In other words, greedy states tend to pursue a band-wagoning strategy instead of balancing. Because they are trying to prevent the balance of power againist themself.
Offensive Realism and Defensive Realism Within the Framework of Structural Realism
Structural Realism is divided into sub-theories, the most apparent of which is Offensive Realism and Defensive Realism. Offensive Realism is the most important representative of Realist theory. It is a competitive type of structural Realism.
It is a kind of theory that argues that power have to be maximized due to prediction of a more competitive world that viewed at the origin of Offensive Realism. It has been mentioned above that the intentions of states are unknown, but Marshaimer also suggests that states should take into account the worst possibility of such intentions and act accordingly. In other words, according to Offensive Realism, to continue to survive, maximizing power is the first measure in term of security.
According to Mearsheimer, there are five major assumptions about why states make war for power and why they want maximum power. The first assumption, Great power or the main actors in world politics and they operate in anarchic system. Second one is all states posses some Offensive military capability. Each state, In other words, Has the power to inflict some harm on its neighbour. Thirdly, States can never be certain About the intentions of Other states. States Ultimately wants to know Whether other states are determined to use force to alter the balance of power ( revisyonist states) Or whether they are satisfied enough with it that they have no interest in using force to change it(status qou states) . Fourht, The main goal of states is survival… Because if State does not survive, it cannot pursue those other goals. Flfth, States are rational actors, Which is to say they are capable of coming up with sound strategies that maximize their prospects for survival. 
However, it should be noted that these are basically assumptions. For this reason, states do not say that they must or will enter into a struggle for power with each other. But according to the third assumption revisionist states create a security dilemma for other states. This can be achieved by maximizing the national power or by balancing the power. For example, after the World War I the revisionist states -such as Germany and Japan- pursued power politics. Thus, they threatened the national interests of other states and causing the security dilemma. In the face of these, Britain had to resort to the balance of power with France and Russia. Therefore, the question of why states are seeking power can be explained by the movements of the states and the structure of the international system.
On the other hand Defensive Realism, unlike other structuralist realist theories, claims that the international system does not have an overly competitive structure. According to Waltz, cooperation and self-restraint will be the best choice for the state under certain circumstances. In contrast to Aggressive Realism, Defensive Realism claims that the international system does not reveal the competitive trend in general.
According to Waltz, who dealt with the Mearsheimer’s maximum power, states are not seeking to maximize their power. Because there is little chance that such efforts will succeed, and even if they succeed, other states will seek to form an alliance against the state that is trying to become hegemon power. Therefore, he claims that too much power is not desirable by states because they knows that effective coalitions will be formed against them.
The main example is whether China’s rapid economic growth will cause competition and insecurity in the international system. First of all, according to the Offensive realism, this situation will cause competition because Offensive Realism predicts the competitive structure and the maximum power. On the other hand, Defencive Realism explain it by China’s stuation. China claims that it does not need to establish dominance in the region and that it will play a deterrent role in the conflict, which could not lead to competition. Consequantly, China’s rapid ecomomic growht could not cause global competition.
In general, however, China’s economic growth has led to a commercial competition even today. Therefore, it is clear that China’s economic greatness, which the United States is trying to counter by taxes, will lead the United States to competition in the long term. At the same time China’s economic growth will concomitant military power and maximum power ambitions in the long term. Thus, the maximum power that China will have will undermine America’s global hegemony. Thereby, today, the United States, which sees China’s rapid growth, will want to prevent China from becoming a great power because it will not want its global leadership to be shaken. Thus this will lead to insecurity and competition in the region and in the global area.
Motivational Realism which includes Classical Realism and Neo-Classical Realism that claims that the basis determinant to understanding international competition and conflict behavior is not international structure, it is structure of each states. In other words, the nature of states determines the international structure and system. For example, in systems where major powers are security seekers, the possibility of cooperation and peace is higher, and on the other hand the possibility of war is higher in systems with one or more greedy states.
In spite of that, according to Waltz, the international system itself produces competition. Thus, different motivations of states do not matter much about the structure of the international relations system. Because the structure already determines the motivation of the state. But Morgenthau, one of the representatives of Classical Realism, says that the basic causes of real competition is nature of human, not structure or system, to the contrary to Waltz. According to Morgenthau, the nature of human is the reason why states seek power, because there are desire for power and selfishness in human nature. Therefore, human want to reach maximum power in an anarchic system where there is no higher authority and then ordinarily this causes competition on a system basis.
In case of states, the main purpose is national self-interest. The author, explains this situation as follows:“ The ambition of the state has other resources, including the desire to increase prosperity and prosperity and to spread its political ideology or religion.” In this context, it can be said that the USSR has shaped the invasion of Afghanistan between 1979-1989 to spread national self-interest and communist ideology. The other example of the same situation is that the US has occupied Iraq in 2003 by highlighting liberal concepts.
The structure of the international system in which Realism emphasizes is of great importance for understanding the relations between states. Looking at the international system, it is seen that the priority of the States is survival. According to Realist theorists, states resort to some security strategies to sustain their lives. Since the main aim is to countinue of state’s survival, it is possible to achieve this goal in different ways according to the situation of the system. For example, it should participate in alliances against a strong state, but in some cases it should be able to survival by self-help. Because, according to Realism, the structure of the international system is anarchic so in the absence of a superior authority, states must take care of themselves.
Waltz, a representative of structural Realism, says that the structure of the international system forces states to compete and that it is difficult to get rid of this competitive environment. Mearsheimer, on the other hand, states that the international system is anarchic and states must reach maximum power in order to provide security. As it seen, because the structure of the international system forces the states to compete, the states have to pay attention to the military power. Motivational Realism claims that the structure of the international system is not completely anarchic and that what determines the system is the motivation of states. Realism focuses on whether the war is likely to occur in a bipolar system or a multipolar system. Given the examples considered in this context, it is understood that the main cause of conflicts in the international system is the desire for power.
Aral, Berdal. Küresel Güvenlikten Küresel Tahakküme: BM Güvenlik Sistemi ve İslam Dünyası . İstanbul, Küre Yayınları, 2016
Balcı, Ali. Gardaş, Şaban. Uluslar arası İlişkilere Giriş. İstanbul, Küre Yayınları, 4. Baskı
Burchill, Linklater, Devetak, Donnelly, Nardin, Paterson, Reus-Smit. Uluslar arası İlişkiler Teorileri. Çev. Rahim Acar. İstanbul. Küre Yayınları. 3. Baskı.
Collins, Alan. Contemporary Security Studies. “Charles L. Glaser, Realism”. Oxford University Press, 2010.2. Edition.
Diri, Esra (ed.), Uluslararası Ilişkilerde Anahtar Metinler 1. Ankara: Uluslararası İlişkiler Kütüphanesi, 2013.
Dunne, Timothy, Milja Kurki, and Steve Smith. International Relations Theories: Discipline and Diversity. New York: Oxford University Press, 2013.
 Collins, Alan. Contemporary Security Studies. “Charles L. Glaser, Realism”. Oxford University Press, 2010.2. Edition. 16
 Collins, Alan. Contemporary Security Studies. “Charles L. Glaser, Realism”. Oxford University Press, 2010.2. Edition. 20
 I.b.i.d. 21-22
 Dunne, Timothy, Milja Kurki, and Steve Smith. International Relations Theories: Discipline and Diversity. – Richard Ned Lebow, Classical Realism. New York: Oxford University Press, 2013. 72-74
 Aral, Berdal. Küresel Güvenlikten Küresel Tahakküme: BM Güvenlik Sistemi ve İslam Dünyası . İstanbul, Küre Yayınları, 2016. 235-236
 Balcı, Ali. Gardaş, Şaban. Uluslar arası İlişkilere Giriş. İstanbul, Küre Yayınları, 4. Baskı. p.128-129
 Collins, Alan. Contemporary Security Studies. “Charles L. Glaser, Realism”. Oxford University Press, 2010.2. Edition. 22
 Dunne, Timothy, Milja Kurki, and Steve Smith. International Relations Theories: Discipline and Diversity. – John J Mearsheimer, structural Realism. New York: Oxford University Press, 2013. 78-79
 Collins, Alan. Contemporary Security Studies. “Charles L. Glaser, Realism”. Oxford University Press, 2010.2. Edition. 24
 I.b.i.d. 28
 Burchill, Linklater, Devetak, Donnelly, Nardin, Paterson, Reus-Smit. Uluslar arası İlişkiler Teorileri. Çev. Rahim Acar. İstanbul. Küre Yayınları. 3. Edition. .55
 Collins, Alan. Contemporary Security Studies. “Charles L. Glaser, Realism”. Oxford University Press, 2010.2. Edition. 28