How did we come to have an international order that is so radically protective of the status quo?
Anything so widespread and deeply entrenched as today’s prohibition against annexation by conquest is a product of many different factors coinciding. One of the most puzzling things about it is that those who seem most capable of conquest on a large scale are some of the biggest opponents of forcible territorial expansion. It is no surprise that conquest is deplored by victims of conquest, such as Palestinians or Ukrainians, or those who could become victims of conquest, such as Estonians or Taiwanese. The interesting question is why, for example, the United States, still by far the world’s largest military force, is a major proponent of the rule against annexation by conquest. The US maintains military force on every continent in the world and uses it frequently, but not since annexing the Northern Mariana Islands, which it conquered during the Second World War, has the US annexed conquered territory. Why would the world’s only superpower tie its own hands in this way?
The answer to this question, in part, derives from the driving forces that made up the US from its beginning: a particular brand of settler colonialism, driven to continental dominance by the thirst for land ownership, plantation slavery, and agricultural and later industrial capitalism. Up to around 1900, the US engaged in relentless territorial conquest. In this respect, it was like many other empires in world history, but one thing that set it apart from other historical empires was the degree to which its conquests were driven by groups of settlers expanding more or less of their own initiative. Before the US became independent, while it was still a part of the British Empire, the British had tried to restrain settler expansion, which had earlier provoked expensive wars that threatened the European state system with instability. When the US achieved independence, the new federal government was less committed to honouring territorial agreements with Indigenous peoples than the British had been. Still, the federal government struggled to regulate the chaotic westward advance of settlers. A perhaps surprising number of states (California, Florida, Hawaii, Texas and Vermont) experienced a short life of independent sovereignty, before joining the US. And those were only the successful ones: plenty of Vermont-like entities sprang up in the Appalachians that never received official recognition, with names like Vandalia, Watauga, Transylvania, Westsylvania, and so on.
