War is in its two-thousandth year of extinction.
It is always being declared dead, a sign of cultural progress, and certainly world wars have declined - since World War II, Europe has enjoyed its long period of peace in its history. But whether or any actual war between nations has declined is debated by political scholars.
Nations would like to wage war, they are eager, says Bear Braumoeller, author of a paper at the annual meeting of the American Political Science Association and associate professor of political science at The Ohio State University, but fewer conflicts than in the past are instead because nations have an inability to fight rather than an unwillingness to do so.
"As empires fragment, the world has split up into countries that are smaller, weaker and farther apart, so they are less able to fight each other," Braumoeller said. "Once you control for their ability to fight each other, the proclivity to go to war hasn't really changed over the last two centuries."
Steven Pinker in his 2011 book "The Better Angels of Our Nature: Why Violence Has Declined", declared that we were outgrowing war. As evidence, Pinker pointed to a decline in war deaths per capita. But Braumoeller believes that is a flawed measure.
"That accurately reflects the average citizen's risk from death in war, but countries' calculations in war are more complicated than that," he said.
Moreover, since population grows exponentially, it would be hard for war deaths to keep up with the booming number of people in the world.
Because we cannot predict whether wars will be quick and easy or long and drawn-out, a better measure of how warlike we as humans are is to start with how often countries use force -- such as missile strikes or armed border skirmishes -- against other countries, he said.
"Any one of these uses of force could conceivably start a war, so their frequency is a good indication of how war prone we are at any particular time," he said.
Braumoeller used the Correlates of War Militarized Interstate Dispute database, which scholars from around the world study to measure uses of force up to and including war. The data shows that the uses of force held more or less constant through World War I, but then increased steadily thereafter.
This trend is consistent with the growth in the number of countries over the course of the last two centuries. But just looking at the number of conflicts per pair of countries is misleading, he said, because countries won't go to war if they aren't "politically relevant" to each other.
Military power and geography play a big role in relevance; it is unlikely that a small, weak country in South America would start a war with a small, weak country in Africa.
Braumoeller says that once he took into account both the number of countries and their political relevance to one another, the results showed essentially no change to the trend of the use of force over the last 200 years.
While researchers such as Pinker have suggested that countries are actually less inclined to fight than they once were, Braumoeller said these results suggest a different reason for the recent decline in war.
"With countries being smaller, weaker and more distant from each other, they certainly have less ability to fight. But we as humans shouldn't get credit for being more peaceful just because we're not as able fight as we once were," he said.
"There is no indication that we actually have less proclivity to wage war."