International relations, or the relationships and interactions between different nations and ethnicities, is inherently complex, both in practice and as an academic discipline. Since the publication of Kenneth Waltz's Man, the State, and War in 1959, scholars and diplomats have found it useful to think about the numerous factors that shape international relations by breaking them into different levels of analysis -- individual, state and international. These different levels of analysis illuminate different reasons for why countries go to war, sign treaties or pursue alliances -- is it due to the personalities of individual leaders, the values of particular nations as a whole or the characteristics of the international system as a whole?

International or Systemic Level

The international or systemic level of analysis argues that all foreign policy can be understood without even looking at the internal characteristics of nations or individuals. Rather, characteristics of the international system lead nations to behave in particular ways based upon how much power they hold. The most easily understood example of international level analysis is the Cold War, when there was a bipolar system where two nations -- the United States and the USSR -- both held substantial power. When two nations hold the majority of international power, there will inevitability be tensions between the two nations, and all their decisions will be based on maintaining their power among nations and preventing the other nation from gaining more power. As China gained power in the 1970s, a tripolar system emerged, and no one wanted to be the "odd man" out, with the other two nations allied against the third. The Unites States used this to its advantage by reopening relations with China and thus forcing the USSR's hand in diplomatic relations. A more modern example would be U.S. intervention in Iraq; supporters of international level analysis argue that the United States is the only power -- the superpower -- in a unipolar system, necessitating its military action to demonstrate and maintain its power.

State Level

Supporters of state level analysis argue that the international system level tells only part of the story of international relations, but looking at the backgrounds of states -- type of government, economic performance, geography, history and cultural values -- can offer a more complete explanation. In this view, it is important to note that the Cold War was not just a conflict between two superpowers but that one of the two powers was a democracy. Similarly, the economic systems of the two powers -- capitalist and communist -- are also significant. A state-level analyst could point to the collapse of the USSR's economy in the 1980s as one of the factors leading to the end of the Cold War. The U.S. intervention in Iraq could be explained by the U.S. cultural belief that its political and economic systems are "good" while other systems are "bad."

Individual Level

Finally, the individual level emphasizes the "great man in history" concept. In this view, the very personalities of leaders shape foreign policy. Leaders are not simply mechanically responding to international or state systems, but taking an active role in determine international relations. Perhaps the most obvious example of a individual level analysis is explaining World War II through Adolf Hitler's leadership; another would be when scholars attribute the end of the Cold War to the relationship between President Reagan and Soviet leader Gorbachev. Once again using the Iraq War example, an individual level analysis would examine the character and ideology of George W. Bush, Donald Rumsfeld, Dick Cheney and other key players in influencing the U.S. military action.

Marxism and Levels of Analysis

Most theories of international relations fall into one of the three levels of analysis. Marxism, however, does not rely simply on individual, state or international levels, but sees class as the category that underlies all political relations. Decisions are made by power brokers who are members of the ruling, or elite class. The wealthy, capital-holding class exerts power over the working class, and will continue to do so until the working class gains control over the means of production. On an international level, imperialism is also explained by class relations. In the late 19th and 20th centuries, capitalist nations needed raw materials as well as outlets for their factory-made products. These factors led to the imperialist foreign policies of most of Western Europe, something that Marxists argue has continued to shape international relations today through the international financial oligarchy of multinational banks and corporations. In the Marxist view, it is class relations that motivate and underlie decisions at the individual, state and international levels.