Geopolitics: Alliance Theory
Why Nations Befriend Their Enemies' Enemies (And Why It Always Gets Complicated)
The most reliable rule in geopolitics isn't about ideology, geography, or economics — it's about who threatens whom right now.
The Idea
There is a principle so durable it functions almost like a law of political physics: states tend to align against the most powerful or threatening actor in the system, not necessarily with those who share their values. This is the core insight of balance-of-power theory, and it explains alliances that look, on the surface, completely absurd — democratic nations arming authoritarian regimes, bitter historical rivals signing mutual defence pacts, ideological enemies sharing intelligence. The key distinction in alliance theory is between balancing and bandwagoning. Balancing means joining the weaker side to prevent a dominant power from getting too strong. Bandwagoning means jumping on the winning side to share the spoils. Most theorists — following Kenneth Waltz's influential work in the 1970s — argued that balancing is the default behaviour of states in an anarchic international system. If one power grows too large, others coalesce against it, almost automatically, because survival is the first interest of any state. But Stephen Walt refined this in the 1980s by pointing out that states don't just balance against power — they balance against perceived threat. That means offensive capability, geographic proximity, and aggressive intent all feed into who gets targeted by a counter-coalition. A strong but distant power may be tolerated. A weaker but nearby one with expansionist ambitions may trigger an alliance overnight. This is why alliance theory is less about friendship and more about arithmetic — and why alliances forged in one era can become liabilities in the next.
In the World
Consider the diplomatic earthquake of August 1939: the Molotov-Ribbentrop Pact, signed between Nazi Germany and the Soviet Union. To contemporary observers, it seemed to defy all logic. Hitler had spent years defining Bolshevism as an existential civilisational enemy. Stalin had watched Nazi Germany rearm with evident alarm. And yet, for a brief and catastrophic window, they carved up Eastern Europe together. The pact was, in alliance-theory terms, a case of bandwagoning mixed with threat perception. Stalin calculated that the Western democracies — Britain and France — were willing to let Hitler's aggression drift eastward. The Munich Agreement of 1938, which handed Czechoslovakia's Sudetenland to Germany without consulting Moscow, confirmed his suspicion that he was being set up as the buffer. Rather than form a balancing coalition with the West against Hitler, he cut a deal to buy time and territory. Hitler, meanwhile, needed to avoid a two-front war. Neutralising the Soviet Union, temporarily, removed the threat he feared most before he turned west. Both leaders were operating exactly as alliance theory predicts: not from ideology, not from trust, but from a cold calculation of who posed the most immediate danger and what alignment best delayed it. The pact collapsed in June 1941 when Germany invaded the Soviet Union — at which point Stalin immediately became what the theory also predicts: a de facto ally of Churchill's Britain, two men who despised each other's systems, united entirely by a shared and overwhelming threat.
Why It Matters
Understanding alliance theory changes how you read the news. When you see two countries suddenly warm to each other despite apparent ideological differences, or a long-standing alliance start to fray despite shared values, the question to ask isn't 'what do they have in common?' — it's 'what are they both afraid of, and has that fear shifted?' This lens also dismantles the comforting but misleading idea that foreign policy is primarily about ethics or loyalty. Alliances are instruments, not relationships. They endure as long as the threat calculus holds and tend to dissolve — sometimes quickly — when it changes. NATO, for instance, was forged in response to a specific Soviet threat. What holds it together now is a live and contested question, precisely because the original logic has evolved. For anyone trying to understand why the world is arranged as it currently is — why certain countries arm certain others, why historical enemies cooperate on specific issues, why some coalitions feel permanent and others fall apart overnight — balance-of-threat theory is one of the most honest and clarifying frameworks available.
A Question to Ponder
Is there a relationship between countries you've assumed is based on shared values that might actually be held together by a shared fear — and what would happen to that relationship if the fear disappeared?
Get a new one of these every morning.
Start learning with Thinkable