a1 Senior Research Fellow at the Hoover Institution, Stanford University, Stanford, California.
Nations have two methods of increasing their security: building arms and forming alliances. Both methods present different political costs that must be incurred to raise security. Building arms requires shifting economic resources to the military. Forming alliances requires abandoning interests that conflict with those of the ally. Each of these strategies produces domestic opposition. A nation's response to a threat to its security must weigh the relative attractiveness of arms versus allies, both in terms of their effects on internal politics and on their external benefits. Three cases are examined in the light of this argument. The response of Austria and France to the unification of Germany in the 1860s is the central case. Theories of alliance formation based on neorealism and the offense-defense balance predict that Austria and France should have allied against the mutual threat of Prussia. This article argues that they did not form an alliance because arming separately presented lower political costs. World Wars I and II likewise are analyzed from the perspective of the argument above.