A striking number of the world's most persistent, hardest-to-resolve territorial and border disputes trace their origin not to any natural geographic or cultural dividing line, but to administrative borders drawn by colonial powers, often with limited firsthand knowledge of the specific region, and with priorities — administrative convenience, negotiated deals between competing colonial powers, straight lines on a map — that had little to do with the ethnic, linguistic, or religious communities the border would end up cutting across or lumping together.
Borders drawn for the convenience of the powers drawing them
Colonial-era border-making frequently prioritised the practical and diplomatic convenience of the colonial administrators and governments involved over the realities of the populations actually living within the territory being divided. Borders were sometimes negotiated in distant capitals between colonial powers dividing territory between themselves, sometimes drawn as straight lines along lines of latitude and longitude for administrative simplicity, and sometimes shaped by which colonial power happened to control which trading post or garrison at a particular moment, rather than by any careful survey of the ethnic, linguistic, or religious communities already living across the region. The people whose lives the resulting borders would shape most directly generally had little to no say in where those lines actually ended up.
Independence didn't erase the borders, only the authority that drew them
When colonial territories gained independence, the newly sovereign states that emerged generally inherited the existing colonial administrative borders largely intact, rather than redrawing them to better match the ethnic, linguistic, or religious geography of the population — a practice partly driven by a widespread post-independence norm favouring the stability of existing borders over the enormous disruption and potential for endless further conflict that wholesale redrawing would likely have caused. The result, in numerous well-documented cases, is a border that cuts through a single ethnic or linguistic community, splitting it across two or more different states, or alternatively forces multiple historically distinct communities with little shared history of governing themselves together into a single post-independence state — border configurations whose origin lies substantially in colonial-era administrative convenience, but whose consequences, including ongoing territorial disputes and internal political tension, are still being worked through by the states and populations that inherited them.
What we're still unsure about
That numerous contemporary border disputes and internal political tensions trace back to colonial-era administrative borders is well documented and widely discussed among historians and political geographers, with substantial case-study evidence supporting the pattern. What's harder to establish with precision, and varies considerably from case to case, is exactly how much weight colonial border-drawing deserves relative to other contributing factors — post-independence political choices, resource competition, and other historical developments that occurred after independence — in explaining any single specific ongoing conflict, since most real disputes involve multiple interacting causes rather than tracing cleanly back to colonial border decisions alone.
This sits inside International Boundaries & Territorial Disputes, one of seven topics in Geopolitics, one of five domains in Geography, one of seventeen subjects the app can quiz you on.