While Marxism and Realism are distinct theoretical traditions in International Relations, often seen as opposing, they share several surprising commonalities in their analysis of international politics. Both approaches offer a critical perspective on the liberal idealist view of a harmonious international order and emphasize the role of power and conflict.

Firstly, both theories are fundamentally materialist in their orientation, albeit in different ways. Realism, particularly classical realism, emphasizes the material distribution of power (military capabilities, economic strength) among states as the primary determinant of international outcomes. States act to maximize their power and security in an anarchic system. Marxism, on the other hand, focuses on the material conditions of production and the economic structure of society (capitalism) as the driving force behind both domestic and international politics. For Marxists, economic power and class struggle are the ultimate determinants of state behavior and international relations.

Secondly, both approaches share a pessimistic view of human nature and the potential for cooperation. Realists believe that human nature is inherently self-interested and power-seeking, leading to an inescapable struggle for power among states. Cooperation is seen as temporary and instrumental, always constrained by the pursuit of national interest. Marxists, while not necessarily viewing human nature as inherently evil, see the capitalist system as inherently exploitative and conflict-ridden. They argue that cooperation under capitalism is often a facade for the domination of one class or state over another, and true, lasting cooperation can only emerge after a fundamental transformation of the global economic system.

Thirdly, both theories highlight the centrality of conflict in international relations. For Realists, conflict is an inevitable consequence of the anarchic international system and the constant struggle for power and security among self-interested states. War is a recurrent feature. For Marxists, conflict is inherent in the capitalist system, manifesting as class struggle domestically and as imperialist competition and exploitation internationally. Both see conflict as a structural feature, rather than an aberration, of the international system.

Fourthly, both approaches are skeptical of international law and institutions as independent forces for peace and order. Realists view international law and organizations as reflections of state power, serving the interests of powerful states rather than genuinely constraining them. They are epiphenomenal. Marxists similarly see international institutions as instruments of capitalist states, designed to maintain the existing global economic hierarchy and facilitate the accumulation of capital, rather than promoting universal justice or equality.

Finally, both Realism and Marxism are structural theories, meaning they emphasize the overarching structures that shape state behavior, rather than focusing on individual leaders or domestic political systems. Realism points to the anarchic nature of the international system and the distribution of power. Marxism points to the global capitalist system and its inherent contradictions. Both argue that these fundamental structures dictate the range of choices available to actors and largely determine international outcomes.

In conclusion, despite their differing units of analysis (states for Realists, classes/economic systems for Marxists) and their prescriptions for change, both Realism and Marxism offer a critical, power-centric, and conflict-oriented lens through which to understand the complexities of international politics, challenging more optimistic liberal perspectives.