Abstract: Classical realism, the dominant theoretical tradition through the Cold War, emphasizes the struggle for power among all nations. The realist approach states that Russia invaded Ukraine and annexed Crimea for Russia’s own self-interest in gaining more power. In response, many countries view Russia as not trying to work with other nations and wanting to gain power for themselves at all costs. In contrast, norm-based constructivism holds that shared ideas, expectations, and beliefs about appropriate behavior are what give the world structure and stability and that the actions that nations take in the international community, are in response to the situation that they are in. The constructivist thought is that Russia’s occupation of Crimea is seen by many other nations as illegal and in violation of international norms and rules but, nonetheless, it is in response to Russia’s shared interest and identity with Crimea and the Russian people living there. Researching the phenomenon through these two viewpoints has shown that the theory of classical realism provides an accurate explanation of the reasons behind Russia’s decision to invade Ukraine and annex Crimea; the theory of classical realism also explains the international response Russia faced due to their actions in the region.