Introduction: Research and Methodologyeighty-two), and when they did, the minor powers always
exceeded the half-million population threshold. These facts,
combined with the aim of making the new data set compatible
with the existing Correlates of War data, made it appropriate to
maintain the population threshold for the entire 1648 to 1815
time period. The entire list of international system members
and their dates of entry and exit are available in the index.^11
System membership affects the alliance data in several ways.
Alliances created by one system member with one or more
extra-systemic groups are excluded from this data set. However,
if one of these groups gains system membership during the
tenure of the alliance, the alliance is coded in the Correlates of
War data as beginning on the second earliest system entry date
in the alliance.^12 For example, the United Kingdom and Iraq
signed an alliance on June 30, 1930, but Iraq was not a system
member. Therefore, the alliance has been coded as beginning on
October 3, 1932, when Iraq gained system membership. When a
state loses system membership—through civil war, loss in war,
or political union—the alliance ceases to exist for that state. If
only one member of the alliance remains a system member, the
entire alliance is coded as ending.Alliance type
Alliance type defines the level of support that an alliance mem-
ber pledges to other alliance members. Defense pacts (Type I)
commit states to intervene militarily on the side of any treaty
partner that is attacked.^13 Neutrality and non-aggression pacts
(Type II) specify that parties remain militarily neutral if any
cosignatory is attacked. The neutrality pact is usually more spe-
cific than the more sweeping non-aggression pact. Finally,
ententes (Type III) pledge consultation or cooperation, or both,
during a crisis, including armed attack. Broad, sweeping state-
ments that pledge eternal friendship or observations of similar
principles do not qualify as ententes in this version of the
alliance data.
Because the unit of the observation is the alliance itself,
treaty texts that contain multiple alliance obligations are clas-
sified according to the most serious obligation. However, sepa-
rate treaty texts that pledge different levels of cooperation and
whose durations overlap extant alliance bonds are considered
separate alliances. For example, a text that obligates members
to defend each other if attacked and also pledges consultation
is considered a defense pact. But alliance members that in
March pledge to consult and in May pledge to defend each
other in case of attack are considered members of both an
entente and a defense pact unless the defense pact replaces the
prior agreement.Alliance duration
In determining the effective dates of alliance, the start date cor-
responds with the signature date of the treaty, even though rati-
fication may have come much later. Alliances not ratified are
excluded from the data set.
Termination dates are more difficult to determine, although
end dates could be either specified in the agreement, the result
of a formal abrogation, the result of informal abrogation via
explicitly recognized violations of the terms of the treaty, or via
the assumption of new and incompatible obligations by one or
more of the signatories (Singer and Small 1966). Many treaty
texts state that alliances will last “in perpetuity” or will belvii- Singer and Small identify twenty-three states as system members in
- At least seven of these twenty-three qualified as major states
prior to the 1815 period and are, therefore, considered system mem-
bers at least from the point at which they achieved major status.
Wüurttemberg crossed the population threshold at least by 1759 (ex-
trapolated from two data points fifteen years apart). Baden, Hesse
Electoral, and Hesse Grand Ducal were recognized by France and Great
Britain by treaty in 1803. The United States was recognized as an inde-
pendent state by 1784. All other states met both criteria for minor
status by 1648.
The three states of Genoa, Poland, and Venice are included in the pre-
1815 data even though Singer and Small omit Genoa and Venice from
their lists of system members and include Poland only after 1919.
These states met the Singer and Small criteria in periods prior to 1815
but not afterward (that is, they fell from system membership either
permanently or for some time). For these three states, the system entry
date signifies the date the population threshold was reached (because
all had achieved diplomatic recognition). The exit date lists the point at
which the state fell to conquerors (Poland) or was incorporated into
another state (Genoa and Venice), that is, when the state failed to meet
one of the three criteria for system membership.
Poland also presents a special case for another reason. For most of the
period following the War of Polish Succession (1733–1735) to its final
dissolution in 1795 (by the Third Partition), Poland was under the lim-
ited control of an absentee Saxon king directly influenced by Russia
(Pogonowski 1987; Langer 1972). Even though the Polish nobles did
not have total control of their foreign policy during this period, the
year 1795 remains as the exit date because most foreign policy deci-
sions were still made on Poland’s behalf as a separatestate. All of the
treaties during this period, for example, were made explicitly by
“Saxony-Poland.” This period in Poland’s history is assumed to be sim-
ilar to its eventual post–World War II future under communist rule,
that is, foreign policy decisions influenced by the Soviet Union but
with Poland still a separate state. - The alliances are always listed according to the date of signature in
these volumes. Treaties made by entities that never achieve system
membership during the tenure of the treaty are excluded from the Cor-
relates of War data set and are not listed in these volumes.
13. Leeds et al. (2002) detail the exact obligations and provisions re-
quired for each treaty member according to the alliance treaty. As such,
they code treaties that require military cooperation outside the borders
of the member states as agreements that carry offensive obligations.
Many of these treaties also include provisions for the defense of one or
more state in case of attack and are included in the Correlates of War
data set as defense pacts. As with the original formal alliance data sets
(Singer and Small 1966; Singer and Small 1968), treaties that include
only offensive obligations are excluded from this data set.