After a low point in the early 2000s, the global arms trade is experiencing a resurgence. Powerful states such as the United States, Russia, France, Germany, and China account for the vast majority of the total exported arms but trading weapons technology seems inherently risky. It increases the proliferation rate of technology and creates vulnerability if a trading partner defects from an alliance. Given the risk, why do great powers trade their weapons? The results show a positive linear relationship between great power competition and the volume of arms trade globally. Positive relationships were also found for alliances, domestic regime similarity between importing and exporting states, and for when the importing state is involved in an active conflict. This dissertation looks at the international arms trade using a mixed methodological approach. Quantitatively, a time series multivariate regression model using country year dyads between the major exporting states and all of the other states in the international system is developed to look at how great power competition, alliances, political regimes, and conflict affect the arms trade. The quantitative analysis is supported with two qualitative case studies that employ process tracing to provide more detail about how the international arms trade is related to great power competition, alliance formation, domestic political regime similarity, and conflict. In the first case study, the end of the Cold War is used to show how the decline of the Soviet Union created new arms trade and alliance opportunities for NATO. The second case study looks at the iterative Arab-Israeli War to see how domestic political regimes and conflict affect the arms trade when two great powers compete via proxy in a regional conflict. The levels of great power competition are currently increasing as China continues to mature into a dominant regional power and Russia pursues a grand strategy of agitating against western institutions. Based on the conclusions of this study, this suggests that the level of arms traded in the international system will continue to increase as great powers seek to add to and solidify their alliance spheres of influence by increasing access to their arms.