Alliance Formation in Regional Space: Shifting the Battlefront Between Competing Powers

We study alliance expansion: two great powers at opposite ends of the geographical spectrum sequentially extend a military alliance. At each stage, the great powers can make one offer to a country that is adjacent to this power‘s existing alliance. The process comes to an end because either there are no non-allied countries left to acquire or because some countries refuse to enter. Then, military conflict might occur with some probability. The conflict allocates the benefits of victory and the costs of defeat between the great powers, and it allocates collateral war damages in terms of physical destruction and civilian deaths to the front states of the fight. A country might enter an alliance as a front state, but enlargement of the alliance may shift this role to further accession countries. In equilibrium all small countries are absorbed into two alliances of equal size and, in total, the small countries pay entry fees which are multiples of the collateral damage of being a front state. Cold War as well as NATO expansion after the collapse of the Soviet Empire motivate and illustrate the theoretical analysis.