The Rise and Fall of the Great Powers 30 Years Later:

What has changed since Paul Kennedy's famous work ?

May 20, 2023

One of the reasons I became interested in economic history is due to the work of Paul Kennedy. In particular, back in high school, I read his magnum opus: “The Rise and Fall of the Great Powers” (published in 1987). The book caught my attention with Kennedy’s interesting theories regarding the rise, decline and fall of great powers. Now technically the book is, in its own words, not a “direct work of economic history”. Though I suppose at the very least it is a work dealing with the various economic and military forces that have constantly rearranged the concert of the great powers. Whatever you classify it as, it remains one of my favorite books.

In his work Kennedy surveys the geopolitical landscape from the year 1500 to the late 1980s. Beginning with the state of the world in 1500 Kennedy examines several core regions: Russia, Japan, China, Europe and the Middle East. He also puts forth his reasons for why the great powers of the early 1500s (the Ottoman Empire and Ming China) failed to keep pace with the emerging might of Spain, Portugal, France and so on. Kennedy’s primary reason is that the Ottomans and Chinese fell behind due to internal political decisions that resulted in their isolation and eventual eclipsing by the rest of the world. This makes some sense when one considers how different history would have been had the voyages of people like Zeng He continued.

Kennedy's main thesis is roughly summarized as “the relative strengths of the leading nations in world affairs never remain constant, principally because of the uneven rate of growth among different societies and of the technological and organizational breakthroughs which bring a greater advantage to one society than to another.” That is, economic growth is the underpinning of all military and geopolitical power. The reason great nations rise and fall is that some nations become wealthier than others and as such become more powerful.1 More precisely “wealth is usually needed to underpin military power, and military power is usually needed to acquire and protect wealth.” Of course the acquisition of wealth and power induces problems because as states increase in size, they must also devote more resources to the maintaining and expansion of said power. This results in the over-expansion and eventual decline as other states (not yet burdened with a vast military industrial complex) are able to come to the fore. Essentially a great power is faced with the problem of whether to put resources into “guns, butter or investments”. The potential over expenditure on one component risks robbing the others of much needed labor and capital.

Evidently this theory works within the context of the book and Kennedy does a good job providing evidence for it. The evidence comes in the form of a tour of the great world empires of the last 500 years, including the Hapsburgs, France under Louis XIV and Napoleon, the Portuguese, the Dutch, and so on. Kennedy explains how each of these great powers drew their strength (primarily) from economic stability, durability and available resources. Furthermore, great powers fail when the underlying economic strength is no longer able to support the military capacity necessary to remain a great power. So for example Napoleonic France fell because it simply ran out of resources to fund Napoleon's Grande Armee. It did not matter how good of a general Napoleon was, the French simply did not have the resources to fight all four of the other great powers simultaneously. Likewise the Dutch empire, despite being supported by a financially well-off and economically sophisticated state, combined with the genius of admirals like de Ruyter, could not stand up to the far larger might of the emerging British empire.

Before getting to my main point I think it is worth mentioning that the book concludes with forecasts for the fates of the Soviet Union, China, Europe, Japan and the United States (the timing of the book is slightly unfortunate, it was published shortly before the collapse of the Soviet Union which perhaps muddles the predictions somewhat). To give credit to Kennedy, many of his predictions turned out to be rather accurate. Though they do cover a wide range of validity, ranging from prescient, say Japan's problems with an aging population and rival economic powers in Asia, to substantially erroneous, “it is likely [the Japanese economy] to expand faster than the other major Powers in the future”. Regarding the United States Kennedy successfully predicts that the US runs the risk of imperial overstretch and dealing with the obligations and interests that outstrip its military capacity (this is something that has become increasingly apparent in recent years). He also correctly predicts that America will continue to have troubled and difficult relations with the Middle East. Finally Kennedy predicts that the US will increasingly strain under the burden of social inequality and “class politics”. We don’t have time to go through the rest of the predictions here but when people like Philip Tetlock have shown how difficult it is to make predictions even a few months into the future, the fact that a lot of Kennedy’s ideas are still accurate 30 years after the fact is credit to his achievements.

However I think there are some problems underlying the theory of the book. One is that it is problematic to generalize Kennedy’s ideas to pre-modern states. Perhaps this is not an entirely fair criticism given that the book focuses on the years 1500-1980. Moreover I suspect that part of the reason for Kennedy starting in the year 1500 is that a) it is a nice starting point and b) starting from roughly this point we have decent historical economic data. However data collection and analysis has come a long way in the 30 years since the book’s publication. The whole field of economic history has changed, (for instance something like, “Was the Wealth of Nations Determined in 1000 BC '' Comin, Easterly and Gong (2010), which looks at the technological achievements of nations in the years 1500 CE, 1CE and 1000 BCE). Let alone the advances in computing power which allow for more in-depth analysis of many of the empires Kennedy looks at. Now a lot of this data isn’t perfect, even for things like population estimates of major historical cities, say Rome or Ctesiphon, we have to rely on intuition and approximations (some people deride these as guesswork but that is perhaps too harsh).2 However applying this new data (albeit not entirely extensive) to historical empires leads to some questions. For instance consider the following chart from Fouquets and Broadberrys “Seven Centuries of European Economic Growth and Decline” (2015):

Curiously it appears that Spain was the poorest country in Europe over the time frame for which it was supposed to be the dominant power on the continent (1500-1648). So given that economic power is supposed to be source of military power, then the fact that countries like Spain and Portugal are so dominant despite being relatively poor is concerning. Perhaps we could explain this problem away by saying the Spain and Portugal were initially dominant because they were the first European countries to get into the empire business and it was only once other countries like England got involved that they fell apart. I am not sure how much I buy this explanation though. Perhaps a better explanation is that Spain’s population was far larger than England’s and as such its total GDP was far larger than England’s even if it is much smaller in per-capita terms.3

The above could be considered minor details, but my broader concern is that Kennedy’s theory fails when one looks at the collapse/fall of pre-modern empires. For example consider the Achaemenid and Sassanid Persian empires. The Achaemenid empire, which ruled an area stretching from Egypt to India only fell apart because a Macedonian king named Alexander invaded and conquered it (around 330 BCE). Likewise the Sassanian empire fell in the early waves of the Islamic conquests (approximately 630-650 CE). Neither of these states fell due to too much expenditure on military might and hence economic decline. Rather they both succumbed to outside conquerors from backwards regions of the globe that in no way posed a significant economic (and supposedly military threat) to the established world order.4 There are more examples as well, for instance the thalassocratic empires of Venice and Athens owe a large degree of their decline to military defeats on the seas.

In all fairness, Kennedy’s theory works well for other ancient states. For instance the fall of the Western Roman Empire (traditionally dated at 476 CE) can be partially explained by Kennedy’s work. Namely in the wake of the reforms of Diocletian (ruled 284 - 305 CE) and Constantine I (ruled 306 - 337 CE) the Roman bureaucracy and military expanded by a significant percentage. The military doubled from roughly 300,000 to 600,000, and the bureaucracy went from around 300-400 to 40,000 (these numbers are disputed; I got these from Warren Treadgold’s “A History of Byzantine State and Society”). Now some of the ways the government paid for this drastic increase was by occasionally debasing the coinage though this had its problems namely, rampant inflation. The preferred alternative was taxation. The increase in taxes, bureaucracy and military worked for a while but eventually the system started to break down. Namely in the wake of increased barbarian invasions around 400 CE local elites and magistrates realized that the Roman Empire could no longer protect them and hence stopped paying taxes to the government. Since the government stopped getting taxes then the army could no longer be paid, since it was at this point entirely composed of barbarians they went into business for themselves and carved up the Western Roman State.

The above is of course a broad generalization and simplification, but overall it does fit in with Kennedy’s theory, namely the increase in military expenditure led to economic problems which contributed to the fall of Rome. In this case the opposing states aren’t really states but rather the great Germanic confederations that challenged and eventually overthrew Rome. So the theory works, sort of, if you gloss over the other contributing factors for the decline of Rome such as population decline, barbarization of the army, increasing disputes between East and West and the curious Roman habit of executing successful generals currently holding the empire together (Stilicho and Aetius being the prime examples of this).

Perhaps the main takeaway from all this is that it is difficult to find a single theory that works to explain the rise and fall of great powers across all eras of human history. The world is vastly different from 2,000 or even 500 years ago. The same reasons for the fall of historic states need not be the same reasons for the fall of modern states. This is especially relevant when one considers the fact that the very notion and idea of what a “state” is has changed. Ancient states were vastly different in conception, construction and how their inhabitants perceived them. Something like the modern nation-state has only really emerged in the last couple hundred years or so. Not that Kennedy’s work is the only book that runs into such problems, for instance some of the cliometric work by authors such as Peter Turchin does a better job of explaining the collapse of ancient empires but doesn’t work as well for modern states. The list goes on, none of this means that developing theories to explain the rise and fall of states is futile only that we need to consider both the time period during which these states existed and be wary of applying it to different eras.

Decline and Fall

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