Resources and Methodology

This project is seeking to identify all instances since 1500 in which a rising power threatened to displace a major ruling power. The current Case File includes 16 examples. In identifying and summarizing these cases, we have followed the judgments of leading historical accounts—specifically resisting the temptation to offer original or idiosyncratic interpretations of events.  We began with broad historical summaries including William Langer (An Encyclopedia of World History), William McNeil (The Rise of the West: A History of the Human Community), AJP Taylor (The  Struggle for Mastery in Europe: 1848–1918), Brendan Simms (Europe: The Struggle for Supremacy from 1453 to the Present), and Paul Kennedy (The Rise and Fall of the Great Powers), as well as political science reviews, including Robert Gilpin (War and Change in World Politics) and Jack Levy (War in the Modern Great Power System). Noting all cases in which they identify competition between major rising and ruling powers, we then compared their views with leading accounts of each case (and cite these accounts in each case). Where there were significant differences in interpretation, we have relied on The New Cambridge Modern History as referee.

These histories use “rise” and “rule” as conventionally defined, along with synonyms emphasizing rapid shifts in relative economic and military strength. Most of the cases come from post-Westphalian Europe, although we start our analysis with the Portugal-Spain rivalry that resulted in the 1494 Treaty of Tordesillas. In doing so, we essentially follow the rationale of Levy’s War in the Modern Great Power System, which itself follows a long line of historians in dating the beginning of the “modern system” recognizably in place today to the end of the fifteenth century. Of the 95 inter-state wars since 1816 listed in the Correlates of War Project dataset, six qualify by our criteria.

In Phase II of the project, now underway, we are seeking to identify additional cases—including cases of hegemonic challenges in regional competitions or among less-than-major powers. We are also assembling a catalogue of metrics of national power and searching for data to provide more quantitative indicators of “rise” and “rule.” Because this is very much a “work in progress,” additions, suggestions, criticism, and comments are not just invited, but welcomed.

The use of historical cases for controlled comparison is methodologically complex. Issues include criteria for selection, clarity of independent variables, clarity of dependent variables, and relative weight of similarities vs. differences among cases. For a thoughtful discussion of these issues, we recommend Alexander George and Andrew Bennett, Case Studies and Theory Development in the Social Sciences; Steven Van Evera, Guide to Methods for Students of Political Science; Gary King, Robert Keohane, and Sidney Verba, Designing Social Inquiry: Scientific Inference in Qualitative Research; and the Oxford Handbook of Political Methodology.

We have attempted to include all instances since 1500 in which a major ruling power is challenged by a rising power. In technical terms, we sought not a representative sample but the entire universe of cases. Therefore, as the Oxford Handbook of Political Methodology notes: “Insofar as comparative-historical researchers select what can be considered the entire universe of cases, standard issues of selection bias do not arise.”

In social science terminology, the independent variable in this study is a rapid shift in the balance of power (correlation of forces) between a major ruling power and a rising rival that could displace it. Dominance/primacy/leadership can be in a geographical area (e.g., continental Europe in the 16^thcentury for the Hapsburgs) or in a particular domain (e.g., Britain’s control of the seas in the 19^thcentury). The dependent variable in this inquiry is war, defined according to the standard criteria in the Correlates of War Project as military conflict causing a minimum of 1,000 fatalities per year.

A larger methodological problem for this inquiry is the absence of established metrics for assessing “national power” or the “balance of power.” These terms are regularly used in histories and political science analyses, as well as policy discussions. Yet there are no agreed-upon metrics of national power. Economic capability reflected in GDP provides a substructure for national power. But asking whether state A can cause state B to take actions that it would not otherwise have taken (or forgo actions that it would otherwise have chosen) requires combining judgments about a number of additional factors, including scientific, technical, and organizational infrastructure, and the ability of each state’s government to translate these factors into actions. In such assessments, it is not possible to avoid also making judgments about culture or propensities (for innovation, sacrifice, strategy, or fighting), the authority and competence of governments, ideology (that attracts or repels), and even statecraft.

In addition to objective metrics about one state’s rise relative to another, an important factor in our analysis is subjective perception. For Thucydides, it was not just the rise of Athens, but “the fear that this instilled in Sparta” that led to war. Thus, as we are assembling yardsticks of national power and the best historical data relevant to these metrics, we are also exploring ways to assess how objective changes are reflected in subjective perceptions of power.

This section collects resources related to Graham Allison's Destined for War: Can America and China Escape Thucydides's Trap?

Read related publications and research from Graham Allison and the Belfer Center.

See Destined for War's comparison of the relative weight of US and Chinese GDP.

Take the China quizzes— how did the US and China compare in 1980 versus today? When might the US actually find itself number two?

Download the graphic showing the outcome of all 16 cases in the Thucydides’s Trap Case File.

Read the new Belfer Center report "Freedom of Navigation in the South China Sea: A Practical Guide".

"Compare the relative weight of the US and Chinese economies as if they were two competitors on opposite ends of a seesaw. The conclusion is as obvious as it is painful. Americans have been debating whether they should put less weight on their left foot (the Middle East) in order to put more weight on their right (Asia). Meanwhile, China has just kept growing — at three times the US rate. As a result, America’s side of the seesaw has tilted to the point that soon both feet will be dangling entirely off the ground."

Graham Allison, Destined for War: Can America and China Escape Thucydides's Trap?

Could The US Become Number Two?

"In my national security course at Harvard, my lecture on China begins with a quiz. The first question asks students to compare China and the United States in 1980 with their current rankings. Repeatedly, students are shocked at what they see... The second question pricks more delusions. It asks students: When might the US actually find itself number two? In what year might China overtake the United States to become the number-one auto market, the biggest market for luxury goods, or even the largest economy in the world, full stop?"

Graham Allison, Destined for War: Can America and China Escape Thucydides's Trap?

On this page, you can download a graphic designed by the Thucydides's Trap Project showing the 16 cases from our Case File. The full Thucydides’s Trap Case File can be accessed here.