Changes in the distribution of military power lead to

● Changes in the distribution of military power lead to wars. In other words, wars are just the result of
modifications in the balance of power.
● Robert Jervis (one of the leading scholars in International Relations), formulated the Security Dilemma:
“many of the means by which a statetries to increase its security decreases the security of others”.
○ Suppose that country A creates a new weapon, country A becomes a threat to its neighboring
states. This alters the previous balance of power between the countries; thus surrounding states
of A may decide to attack it in order to take the balance of power back to normal and because
they fear that if A is improving its weaponry it is because it is preparing for a future attack.
● States act to prevent the formation of hegemonic power , balancing externally (through coalitions,
making alliances with other countries) and internally (increasing military capabilities). If every country

invests in military capabilities the probability of a conflict to happen increases. - Spiral: one country
increases its military capabilities, the other one too as they fear an attack and so on until they all have
increased their military power and a conflict happens.
● In more than half of all wars, the contending parties are “enduring rivals”.
● Earlier disputes make later disputes more likely.
● The greater the number of disputes or crises between rivals, the greater the probability that any further
dispute escalates into war.
● “Steps-to-War” model: disputes are more likely to end up in war, particularly if they take place
between contiguous rivals and are about territorial claims (this is particularly valid for the 1816-1945
period).
Examples of altering the balance of power that may lead to attacks:
● When Germany started investing in military power in the 30s.
● When a communist insurgency wins in a developing country and this country allies with the Soviet
Union and this new communist country becomes a threat to the US.
● The increasing power of China is undermining the traditional hegemony of the US and this alteration in
the balance of power, interstate war might take place.
● Basically, whenever a country becomes more powerful than it used to be, another country feels
threatened and generates temptations or incentives to attack.
Rationalist explanations (also called dyadic or bargaining theories of war)
Why do countries go to war if war is always inefficient? In the bargaining of power model, some soft-rationality
is assumed: States are rational and self interested actors that seek security. However, rationalist explanations
require a much more demanding concept of state's rational behavior.
James Fearon - Professor at Stanford University-, “Rationalist Explanations for War”, International Organization
(1995).
The puzzle: “War is always inefficient ex post –both sides would haYe been better off if they could have
achieved the same final resolution without suffering the costs (or by paying lower costs).” (p.383)
If war is always inefficient from economic and social points of view because it implies a destruction of human
life and infrastructure, why is it the case that states don't try to anticipate the outcome of the potential war and
reach an agreement before actually going to war. What prevents states from reaching ex ante agreements that
avoid the costs of war?