The strategic decision-making mechanisms a state has at its disposal to shape and develop its military means of power are complex. Perceptions of the outside world may be particularly problematic because perceptions of threats change. Political decisions which aim to create robust and long-term security strategies where several factors must be taken into account that are largely determined by the interests of other actors can be difficult to understand and explain. The investment in defence set out in Swedish Defence Bill 2020 is a paradigm shift from reducing to enlarging the armed forces This involves a continued investment into a dedicated professional defence, but in combination with conscription, new establishment of regiments, more military units and increased materiel investment. The purpose of this study is to, examine the driving forces and explanatory factors linked to this paradigm shift, where political decisions to enlarge the military are in focus and examined using Graham Allison and Philip Zelikow's three theoretical perspectives on strategic decision-making. The results of this study clearly show that the dominant driving force for the re-expansion of Sweden's defence capability was the deteriorating external situation, which was evident in terms of all three theoretical perspectives. It is also possible to see traces of other driving forces in the bill, such as long-termism, sustainability and the degree of detailed control of the Armed Forces, which demonstrates the complexity of political decision-making about the creation of military power.