This chapter analyzes the explanations offered by historians at different times for the rise and fall of Sweden as a great power. There is no consensus even on when Sweden’s great power status actually began or ended. Moreover, in-depth reflections are rare on the factors that contributed to the realm’s rise or, conversely, to its collapse. The most popular and durable classical explanations emphasized the Swedish search of external security and/or economic interests in the Baltic region. More holistic explanations focus on the military state or asymmetric interaction between the ruler and subjects. The Great Northern War (1700–1721) ended the Swedish great power period; the disintegration took almost a quarter of a century. Russia, which had significantly improved the use of its vast resources, was the single most important factor in the fall of Sweden. Sweden was also vulnerable to simultaneous invasion by multiple enemies, and Sweden’s main weakness was regional fragmentation due to its large size, long borders, and small population. In the peace treaties of 1719–1721, the loss of territory was extensive.