Prior to the twentieth century, states focused principally on securing their borders and maintaining order within them. Size mattered as territory was deemed essential to secure people, materials, and markets. This precipitated interstate competition as states jockeyed for territorial control. During the nineteenth century, the entry of the people into politics, as workers and nations, meant that states became equally concerned with the issue of belonging. The combination of these factors led to the horrors of the two world wars. Thankfully, this was followed by a postwar settlement whereby national borders were more or less fixed and secured, belonging was established, and order was maintained by various means. This chapter explains how this happened.