Even a cursory understanding of human history betrays our horrifically violent past. But the following chart from Our World In Data paints an even more vivid picture of both the frequency and cost of war over the last six centuries alone. (For a larger and zoomable version, click here.)
As The Washington Post explains:
Each circle on the graphic represents an individual conflict, while the size of the circle shows the absolute number of military and civilian fatalities. The rate of deaths per 100,000 people is shown on the vertical axis — a measure which reflects not just of the conflict’s size, but also how much of the world’s population was involved. The horizontal axis shows the year of the conflict, from 1400 onward. The red line shows a 15-year moving average for the military and civilian death rate, while the blue line is the military death rate for 1946 to 2013.
The first and second world wars stand out as particularly devastating, as does the Genocide of the Jews in the 1940s, the Napoleonic Wars of the 19th Century, and the Thirty Years’ War of the 17th Century. As Roser’s blog points out, the trend in recent decades is toward a substantial decline in death and violence.
One thing the chart does not factor is in the proportional rate of death — e.g., the percentage of a population killed by warfare. Conflicts that would be considered small-scale by today’s standards wiped out huge swathes of an area; for example, the Thirty Years’ War resulted in around 8 million deaths, far less than either world war, but a much bigger chunk of Europe given how much smaller its population was at the time (indeed, much of what is today Germany saws losses of anywhere from a quarter to nearly half of the pre-war population).
By the same token, the smaller conflicts that were the norm around the world before the 15th century were also often more devastating in terms of their frequency and relative fatality rates. This is examined at length in the 2011 book, “The Better Angels of Our Nature: Why Violence Has Declined“, by Steven Pinker, which backs the finding of the chart above — violence and conflict on a large scale, while still a scourge of our species, has declined precipitously over the last century.