The chapter introduces the book by presenting the puzzle it seeks to explain. During the decolonization process, colonial and regional powers frequently pursued the policy of amalgamation to avoid creating micro-states, which resulted in numerous cases of merger. However, some rejected merger projects and became independent separately. What, then, accounts for their separate existence? More generally, why did some colonial areas achieve independence separately from neighboring regions when facing pressure for amalgamation or annexation, while others became part of a larger state? This chapter then elaborates the main line of argument and the theoretical framework that underpins it. It argues that oil and a specific type of colonial administration carved out producing areas to create a state that would otherwise not exist. The introduction ends by briefly discussing methods and explaining the structure of the book.