68 International Relations Theory of War
Table 3.2
The Combined Length of the Six Instances of the Three Different Polarity
Models, 1816–2016
Multipolar Systems Bipolar Systems Unipolar SystemsThe duration of
each of the six
instances of the
different systems
1870–1849=22
1945–1910=36
1848–1816=33
1909–1871=39
1991–1946=46
2016–1992=24
The total duration
of each of the three
polarity models
58 years 118 years 24 yearsThe percentage of
years of each of
the three polarity
models out of the
tested period
58/200=29% 118/200=59% 24/200=12%
The period assessed in the study, 1816–2016, is 200 years in total. In
that period were three instances of the three possible polarity models:
two instances of a multipolar system lasting a total of 58 years—1849–1870
(22 years) and 1910–1945 (36 years)—representing 29 percent of the entire
length of the period; three instances of multipolar systems whose total length
was 118 years—1816–1848 (33 years), 1871–1909 (39 years), and 1946–1991
(46 years)—which is 59 percent of the total duration of the period; and just
one instance of unipolar systems, whose total length was 24 years, 1992–
2016, representing 12 percent of the entire duration of the period.
Table 3.2 shows a comparison of the combined length of the three
instances of the three possible polarity models in the period assessed in
the study, 1816–2016.
The book defines the different instances of the three possible polarity
models in 1816–2016 in a different way from the one in which they are
defined in most theoretical studies in international relations research. In
the existing studies, a common division is into three periods.
1816–1945: Waltz argues that in this period, there was a multipolar system
and there were always five or more powers.^2 Mearsheimer also argues that
there was multipolarity in those years. However, he makes an original dis-
tinction between balanced multipolar systems, 1815–1902 and 1919–1938,
and unbalanced multipolar systems, 1903–1918 and 1939–1945.^3 Schweller