Introduction: Research and Methodology
members have to be independent nation-members of the inter-
national system (for example, so-called alliances between inter-
national terrorist organizations do not qualify), and second, a
treaty text has to exist that identifies a militarycommitment
that is defensive, a neutrality arrangement, or an “understand-
ing” such as an entente (Singer and Small 1966). Lists of the
alliances that meet these criteria have been printed in various
forms (Singer and Small 1966, 1968, 1972; Small and Singer
1982; Gibler and Sarkees 2004). A current listing is available
from the Correlates of War project.
Alliances, Peace, and War
Traditional international relations theories have associated
alliances with both peace and war. Alliances that “correctly” bal-
ance the system are supposed to lead to peace, while incorrect
balancing makes war more likely. This section describes these
theories.
Alliances and Peace?
Alliance theory originally developed as an extension of balance
of power theory; alliances were formed to make sure that the
capabilities of major state coalitions remained relatively equal.
Equality of power was believed to promote peace because it was
thought that no sane leader would risk a war if there was a 50
percent chance of losing; war comes with preponderance, that
is, when a state has an easier chance of winning. At the state
level each nation has the choice to either arm itself or pursue a
policy of alliances when confronted with the prospect of a pos-
sible threat (Most and Siverson 1986; Walt 1987; Waltz 1979). If
a nation chooses to arm, it risks an endless spiral of increasing
armaments that could result in an arms race. According to bal-
ance of power theory, choosing alliances allows states to
respond more quickly and with more precision to increased
threats from other states. Diplomats and international leaders
are able to use alliance networks to properly balance the capa-
bilities of opposing nations to maintain peace in the interna-
tional system. Alliances, in this framework, function only to
serve the balance of power.
Alliance commitments are also said to reduce the level of
uncertainty in the system and minimize the likelihood of war
that may result owing to misperception and miscalculation
(Singer, Bremer, and Stuckey 1972, 23). These commitments
can also reduce the chances of catastrophic shifts in the systemic
balance of power (Osgood 1967, 86). Some balance of power
theorists claim that alliances are also necessary to avoid the
most dangerous wars. A belligerent world power, seeking domi-
nation of the system, would likely restrain itself when con-
fronted with an alliance system poised against it. Alliances, then,
are an indispensable means of maintaining equilibrium in the
system (Gulick 1955, 61–62).
Alliances are also thought to preserve peace in other ways.
Major states may use alliances to constrain revisionist alliance
partners, or an alliance can preserve peace by enhancing the
prestige of a failing power whose collapse could be destabilizing
to the international system (Liska 1962, 31–32, 37–40). Many
neo-realists argue that these alliances become meaningless in
periods of bipolarity because the major state has enough capa-
bilities to ignore the belligerent policies of its weaker allies
(Waltz 1979, 169). Nevertheless, even intense periods of bipo-
larity have seen the growth of intricate alliance systems.Alliances and War?
Waltz’s observation that the major state must have enough
power to ignore the policies of its allies was a response to anec-
dotal evidence that weaker allies tended to bring major state
allies into expanded wars—an observation that has since been
confirmed by more systematic investigations (Siverson and
King 1979, 1980; Yamamoto and Bremer 1980).
That minor states bring major states into war is only one
hypothesis linking alliances to war in the traditional literature.
Traditional arguments linking alliances to war are as numerous
and varied as those associating alliances with peace. For exam-
ple, a state seeking alliances to show resolve could be interpreted
by another state as attempting a strategy of encirclement. The
targeted state would naturally respond by seeking counteral-
liances (Kaplan 1957, 24; Wright 1965, 774). Although such
alliance partners may have been hard to find prior to the sign-
ing of the initial alliance, the developing cleavages could make
other states more likely to become involved (Ray 1995, 375).
The polarized system or region could also simply clarify the sit-
uation and make it easier for the aggressor to determine its odds
of winning. As Bueno de Mesquita (1981, 151) notes, “The
reduction of uncertainty brought about by such information
may be all that is needed to facilitate an aggressor’s desire to
attack another state.”
Balance of power theory can also support the existence of
large, systemwide wars against potential dominance caused by
alliance formation. In the example given above, the revisionist
state is seeking dominance of the system but is confronted
with an alliance against it. Instead of being rebuffed by this
alliance, the revisionist state continues its policies and fights
the war.^1 As Levy (1989, 230) notes, a number of general wars
during the past five centuries appear to fit this proposition.
These include the “wars against Philip of Spain in the late six-
teenth century, against Louis XIV in the late seventeenth cen-
tury, against revolutionary and Napoleonic France a century
later, and against Germany twice in this century” (Levy 1989,
230–231).
As is obvious from these debates, no clear understanding of
the relationship between alliance formation and war has everl- The revisionist fights for a number of reasons (even if its capabilities
do not match those of the coalition against it): the adversaries show a
lack of resolve, the revisionist state is risk acceptant, or perhaps the re-
visionist believes a surprise attack could swing the balance of power in
its favor.