When Do Power Shifts Lead to War?

My article “Known Unknowns: Power Shifts, Uncertainty, and War,” (co-authored with Alexandre Debs) is now officially forthcoming in International Organization. Here is the abstract:

Large and rapid power shifts resulting from exogenous economic growth are considered sufficient to cause preventive wars. Such power shifts are rare, however. Most large and rapid shifts result from endogenous military investments. In this case, preventive war requires uncertainty about a state’s investment decision. When this decision is perfectly transparent, peace always prevails. A state’s investment that would produce a large and rapid power shift would prompt its adversaries to launch a preventive war. Internalizing this, the state is deterred from investing. When investments may remain undetected, however, states may be tempted to introduce large and rapid shifts in military power as a fait accompli. Knowing this, their adversaries may strike preventively even without unambiguous evidence about militarization. In fact, the more effective preventive wars are, the more likely they will be launched against states that are not militarizing. Our argument restricts the role of commitment problems and emphasizes the role of imperfect information as causes of war. It also provides an account of why powerful states may attack weaker targets suspected of military investments even in the absence of conclusive information. We illustrate our theory through an account of the 2003 U.S.-led invasion of Iraq.