Just two decades after World War I, Europe once again erupted into a massive war, despite the implementation of new safeguards like the League of Nations. The three perspectives each offer insights as to why this occurred.

The realist perspective tends to view World War II as the continuation of World War I because the basic problem, the unstable balance of power in Europe, was the same in both cases. For realists, new solutions to war and conflict, such as the League of Nations, exacerbated the problem by turning attention away from the balance of power.

For the liberal perspective, on the other hand, the balance of power itself was the problem, and collective security was the best possible solution. However, the League of Nations failed – and with it the possibility of collective security – due to poor participation and inherent institutional weaknesses.

Finally, the identity perspective examines the phenomenon of nationalism during the interwar period, concluding that nationalism based on racism, xenophobia, and revenge caused aggressive behavior that eventually led to World War II.