Ukraine giving - short term high leverage

Abstract

Since WW2 the world has enforced a norm against states invading other states and taking their territory. The main reason this occured is that military power became concentrated in a cartel of a few large states (US, UK, France, the Soviet Union). These states were pretty tired of wars, and also did not want smaller states to unify and challenge them. Effectively, each of the big 4 (China eventually joined) agreed to stop their own clients from making territorial war. By territorial war, I mean that if you won you had to give back the clay you took, or release it as an independent state (as in the Bangladesh Liberation War). This was stunningly effective, and the the drop in the number of territorial changes around 1946 is actually really astonishing.