James Fearon’s 1995 paper is among the most assigned texts in international relations

The puzzle

In his 1995 article, Fearon seeks to answer why wars happen if they are so costly.

He begins by outlining three possible explanations:

Irrational - people, including leaders, do not act in their best interest because they misunderstand the consequences of their actions, due to factors like emotions or cognitive biases.
Rational - leaders who decide to go to war have personal self-interest (private incentives) that is not aligned with the population and are isolated from negative consequences.
Rational - leaders consider the negative consequences of war yet still decide to engage in it.

The article seeks to explain the mechanisms that result in #3: that is, what prevents rational actors from coming to an agreement, which is almost always preferable to both sides vs. war.

Definitions and assumptions:

Rational actor = an actor that has stable preferences, seeks to maximize them, and incorporates new information
Unitary state actor = a state acts as a single decisionmaker (domestic politics and deliberations are ignored or collapsed)
States are risk averse and prefer non-violence

What doesn’t explain outbreak of war

Fearon first examines existing explanations in IR literature about outbreak of war, revealing some of the factors to be incomplete, insufficient, or special cases of something else:

Anarchy - lack of international enforcement, i.e. no world police
Expected benefits of war greater than expected costs
Rational preventive war
Rational miscalculation due to lack of information
Rational miscalculation or disagreement about relative power

He shows that 1–2 do not explain war, because they do not, by themselves, explain why rational actors don’t bargain and come to an agreement that is preferable to fighting, while #3 is better understood as a special case of a broader commitment problem. Meanwhile, 4–5 address mechanisms for war, but they do not fully explain why rational actors fail to communicate credibly or engage in diplomacy to avoid costly miscalculations.

What mechanisms explain why rational actors initiate war?

Fearon proposes three explanations for why rational actors decide to initiate war. These explanations are not necessarily novel, but rather mechanisms that expand on or reclassify existing ones:

War due to private information and incentives to misrepresent
War as a consequence of commitment problems: at least one side has concerns about another side honoring agreements and future behavior
Issue indivisibilities (less common)

#1 must have two components:

First is uncertainty or misperception about an opponent’s strength or resolve. However, that’s not enough, because a rational actor can engage in different forms of communication to obtain that information.
The second component is failure to resolve these private information problems. One possibility is private information unavailable to the other side, combined with bluffing or misrepresentation. One incentive to bluff is being weaker than the opponent believes. Another incentive to misrepresent your true strength or resolve is that you think the other side will not believe you, and/or it will reveal some military secrets.

An example of asymmetric information contributing to war is Russia-Japan in 1904. Russia pursued an aggressive policy in East Asia and believed it wouldn’t face significant resistance from Japan. Yet Japan had stronger military capabilities and resolve than Russia expected, but saw no credible way to convince Russia otherwise without revealing military secrets. Russia initiated war but lost.

Asymmetrical information narrows the bargaining range.

#2, commitment problems, have several types:

Preemptive war or first-striker advantage, with no credible agreement that can be made to avoid it
Preventive war - one side prefers war now because it fears a less desirable outcome in the future. Another side is not trusted to uphold a bargain in the future and may have an incentive to renege (e.g. Germany and Austria’s concerns about Russia in 1914).
Appeasement and strategic concessions - reaching a settlement is not preferable to war, because another side may ask for more in the future (either because the other side is already strong, and/or the concessions will give them even more of an upper hand). Example: Winter War between Finland and Soviet Union in 1939.

Commitment problems, rather than narrowing the bargaining range, make agreements less credible, especially when there’s no outside enforcement mechanism.

These mechanisms can also interact: for example, uncertainty and bluffing can exacerbate commitment problems.

Note: a formal way to express bargaining is provided at the end.

Conclusions

When a non-violent settlement is preferable to each side, there is a possibility of avoiding war. When a rational actor nevertheless initiates war under this scenario, this must stem from at least one of the following: 1) asymmetrical information or 2) mistrust about the other side’s commitment to honor the agreement and future behavior.

The implication is that any claim of structural causes of war among rational actors must pass through one of the mechanisms above.

Fearon also addresses a couple of anticipated criticisms. First, he acknowledges that actors can be irrational. However, he finds less evidence to support this. He also claims that being clear about rational explanations is necessary to quantify irrationality, which must be in relation to that. Second, multiple factors may be present at the same time in many wars, so how can you distinguish which is the cause? His response is that proposing the mechanisms should come first, and examining which ones are causes or switches must follow that.

What is this good for? And some limitations

Prediction

Fearon presents a comprehensive analytical framework that can be used for retrospective analyses of why rational actors engage in wars. However, as Fearon himself said elsewhere, prediction is still a foundational problem. Existing prediction models rely on structural causes proposed by Fearon and others - incredibly useful for knowing where to look for conditions that increase risks of war - but the “why now?” question remains a challenge. For example, see “War is in the Error Term” by Gartzke (1999).

Russia-Ukraine viewed through the rationalist lens

Some point out the role of asymmetrical information (mechanism #2) in Russia’s decision to invade Ukraine in 2022 - but that’s a partial explanation at best. Another explanation is intangible motivations (nationalism, imperialism) contributing to a commitment problem - preventive war - though not related to security. Instead, the future concern, from Russia’s view, is Ukraine becoming increasingly more democratic and aligned with the West. This framing may help understand “why now-ish”. Another thing worth mentioning is that autocracies dislike democracries partly because they illustrate that a better way is possible, potentially affecting regime stability.

Private incentives in a personalist regime, combined with isolation from negative consequences, is a complimentary rationalist explanation because they affect expected benefits of war. The only difference is unit of analysis: the unitary state actor becomes a single individual.

(Lack of) robust unifying models

Fearon speculates that Hitler is a possible exception to the assumption of rational actors being risk averse and not wanting to fight. If so, the explanatory power of this framework may be weaker when it comes to the deadliest war of the 20th century. It’s striking that even in retrospective analyses, we still don’t a strong unified model of conflict. Reasons cited include lack of empirical data about factors that are hard to observe, including private information, incentives to misrepresent, and intangible motivations. Could more progress be made on the theoretical front with information that’s already available through interdisciplinary approaches?

Fearon (1995) remains an essential read and deserves its place in IR canon. Future posts may cover scholarly contributions related IR since then.

(Optional) Formal expression of bargaining

Suppose you have side A and side B, where:

V_a is the value or benefit of war for side A, and V_b is the benefit of war for side B

p_a is the probability of side A winning, and p_b = (1-p_a ) is the probability of side B winning

c_a is the cost of war for side A, and c_b is the cost of war for side B

The expected net benefit of war for side A is: E_a = V_a * p_a - c_a

The expected net benefit of war for side B is: E_b = V_b * p_b - c_b

Let T = 100 = total value of the issue at dispute (e.g. territory)

t_a is the portion of T that goes to side A in a settlement

t_b = 100-t_a is the portion that goes to side B in a settlement

Then, for a positive bargaining range to exist (i.e. preference for non-violent resolution):

E_a + E_b < 100

Side A prefers a settlement if: E_a < t_a

Side B prefers a settlement if: E_b < t_b

Other ways to express the bargaining range, from the perspective of A:

E_a < t_a < 100 - E_b, or the open interval (E_a, 100 - E_b)

Implications/TLDR:

When a positive bargaining range exists, there is a possibility of a non-violent settlement.

Asymmetrical information narrows the bargaining range.

Commitment problems make agreements less credible, especially when there’s no outside enforcement mechanism.

Costs of war do NOT necessarily have to exceed benefits, for one side to prefer a settlement. The calculation must also account for probability/optimism of winning.

A non-violent settlement will NOT necessarily be fair.

Revisiting a classic: rationalist explanations for war by Fearon

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