"In the late 1800s, Europe had a peaceable bull’s-eye in the northern industrialized countries (Great Britain, France, Germany, Denmark, and the Low Countries), bordered by slightly stroppier Ireland, Austria-Hungary, and Finland, surrounded in turn by still more violent Spain, Italy, Greece, and the Slavic countries. Today the peaceable center has swelled to encompass all of Western and Central Europe, but a gradient of lawlessness extending to Eastern Europe and the mountainous Balkans is still visible. There are gradients within each of these countries as well: the hinterlands and mountains remained violent long after the urbanized and densely farmed centers had calmed down. Clan warfare was endemic to the Scottish highlands until the 18th century, and to Sardinia, Sicily, Montenegro, and other parts of the Balkans until the 20th. It’s no coincidence that the two blood-soaked classics with which I began this book—the Hebrew Bible and the Homeric poems—came from peoples that lived in rugged hills and valleys."