fought in each quarter-century. Once again we see a decline over the five centuries: the great powers have become less and less likely to fall into wars. During the last quarter of the 20th, only four wars met Levy’s criteria: the two wars between China and Vietnam (1979 and 1987), the UNSANCTIONED war to reverse Iraq’s invasion of Kuwait (1991), and NATO’s bombing of Yugoslavia to halt its displacement of ethnic Albanians in Kosovo (1999).
The second dimension is duration. Figure 5–14 shows how long, on average, these wars dragged on. Once again the trend is downward, though with a spike around the middle of the 17th century. This is not a simpleminded consequence of counting the Thirty Years’ War as lasting exactly thirty years; following the practice of other historians, Levy divided it into four more circumscribed wars. Even after that slicing, the Wars of Religion in that era were brutally long. But from then on the great powers sought to end their wars soon after beginning them, culminating in the last quarter of the 20th century, when the four wars involving great powers lasted an average of 97 days.84
FIGURE 5–13. Frequency of wars involving the great powers, 1500–2000
Sources: Graph from Levy, 1983, except the last point, which is based on the Correlates of War InterState War Dataset, 1816–1997, Sarkees, 2000, and, for 1997–99, the PRIO Battle Deaths Dataset 1946–2008, Lacina & Gleditsch, 2005. Data are aggregated over 25-year periods.
FIGURE 5–14. Duration of wars involving the great powers, 1500–2000
Sources: Graph from Levy, 1983, except the last point, which is based on the Correlates of War InterState War Dataset, 1816–1997, Sarkees, 2000, and, for 1997–99, the PRIO Battle Deaths Dataset 1946–2008, Lacina & Gleditsch, 2005. Data are aggregated over 25-year periods.
What about destructiveness? Figure 5–15 plots the log of the number of battle deaths in the wars fought by at least one great power. The loss of life rises from 1500 through the beginning of the 19th century, bounces downward in the rest of that century, resumes its climb through the two world wars, and then plunges precipitously during the second half of the 20th century. One gets an impression that over most of the half-millennium, the wars that did take place were getting more destructive, presumably because of advances in military technology and organization. If so, the crossing trends—fewer wars, but more destructive wars—would be consistent with Richardson’s conjecture, though stretched out over a fivefold greater time span.
We can’t prove that this is what we’re seeing, because figure 5–15 folds together the frequency of wars and their magnitudes, but Levy suggests that pure destructiveness can be separated out in a measure he calls “concentration,” namely the damage a conflict causes per nation per year of war. Figure 5–16 plots this measure. In this graph the steady increase in the deadliness of great power wars through World War II is more apparent, because it is not hidden by the paucity of those wars in the later 19th century. What is striking about the latter half of the 20th century is the sudden reversal of the crisscrossing trends of the 450 years preceding it. The late 20th century was unique in seeing declines both in the number of great power wars and in the killing power of each one—a pair of downslopes that captures the war-aversion of the Long Peace. Before we turn from statistics to narratives in order to understand the events behind these trends, let’s be sure they can be seen in a wider view of the trajectory of war.
FIGURE 5–15. Deaths in wars involving the great powers, 1500–2000
Sources: Graph from Levy, 1983, except the last point, which is based on the Correlates of War InterState War Dataset, 1816–1997, Sarkees, 2000, and, for 1997–99, the PRIO Battle Deaths Dataset 1946–2008, Lacina & Gleditsch, 2005. Data are aggregated over 25-year periods.
FIGURE 5–16. Concentration of deaths in wars involving the great powers, 1500–2000
Sources: Graph from Levy, 1983, except the last point, which is based on the Correlates of War InterState War Dataset, 1816–1997, Sarkees, 2000, and, for 1997–99, the PRIO Battle Deaths Dataset 1946–2008, Lacina & Gleditsch, 2005. Data are aggregated over 25-year periods.
THE TRAJECTORY OF EUROPEAN WAR
Wars involving great powers offer a circumscribed but consequential theater in which we can look at historical trends in war. Another such theater is Europe. Not only is it the continent with the most extensive data on wartime fatalities, but it has had an outsize influence on the world as a whole. During the past