• Earlier: perhaps war is in our genes?
  • Today: could two rational, unitary actors fight?
    • The rationalist puzzle of war
    • Three mechanisms for war
    • Credible threats

Today’s puzzle

Why are sanctions typically unsuccessful in producing compliance with demands (substantial concessions by target only in 20-30% of cases)?

1 The Rationalist Puzzle of War

1.1 The Puzzle

  • War is an inefficient way of settling disputes. War always appears inefficient ex post.
  • Why, then, does it recur? I.e., why does it not always seem inefficient ex ante?
  • Why would two rational actors fight?


  • What prevents states in a dispute from reaching an ex ante agreement that avoids the costs they expect will be paid ex post if they go to war.

  • Note that the same puzzle arises in the context of:
    • Civil court trials. In fact, most civil disputes are settled out of court
      • Both sides can predict reasonably well the damages that might be awared.
      • Lawyers are expensive
      • Most disputes are settled earlier rather than later in the process.
    • Strikes. Most union contracts negotiated without a strike?
      • Prevailing wages in area are generally well known.
      • Strikes are costly to both workers and owners.
      • Both sides have an interest in reaching a settlement.

1.2 Explanation 1: Anarchy

  • Waltz: “In the absence of a supreme authority there is then the constant possibility that conflicts will be settled by force” (1959, p. 188).
  • But if using force is a costly option, why is it ever used? I.e., how does the lack of a central authority prevent states from negotiating agreements both sides would prefer to fighting?

1.3 Explanation 2: Preventive war

  • A decline in power would lead the declining power to attack now
  • Typical story: uncertainty about future motivations


The claim is that without a credible enforcer, war will sometimes appear the best option for states that have conflicting interests.

1.4 Explanation 3: Positive expected utility

  • But again, this does not address the problem!
  • The question is: when will there be bargains that both prefer to war? I.e., can both states have a positive expected utility?


  • There is always an ex ante bargaining range
  • Why might states fail to locate it?

2 Why States might fail to find the ex ante agreement?

2.1 1. Indivisibilities: the problem