__The evidence of history is that no advance which can be applied to the killing of other human beings goes unused. As scientific knowledge continues to explode, it would be naïve, to expect any different. As if we needed any more reasons to confront the role of warfare in our lives, the present supply and future potential of WMDs should convince us that the time has come once and for all to bring our long, violent history of warring against each other to an end.

The nineteenth century was dominated by discoveries in chemistry, from dyes to dynamite. The twentieth century belonged to physics, from subatomic particles and black holes to nuclear weapons. The twenty-first century is set to see great advances in biological knowledge, from our growing understanding of the genome and stem cells to, it’s a shame to say, new and expanded forms of biological warfare. In the past, each iteration of the application of scientific discovery to warfare has produced more horrible and destructive weapons. Sometimes temporary restraint is exercised, as in the successful ban on poison gas in the Second World War, but such barriers burst easily, as the deliberate bombing of civilians in the same war attest.

Human beings have always appropriated new ideas to build increasingly formidable weapons and there is no reason to think that competitive, creative impulse will disappear on its own. As weapons become ever more horrifying—and, with the rise of biological weapons, increasingly insidious—it is no longer enough just to limit the use of one killing technology or another. We need to limit the conditions that lead to war in the first place.

It has become almost a cliché to note that we live in an increasingly complex and interdependent society. But this point is crucially important as we consider the future of war. Our cities once were fortresses, the walled sanctums where our ancestors sought refuge from marauders. The firebombing of the Second World War revealed a new urban vulnerability, but even that insecurity is nothing by today’s standards. We live in giant cities, supplied with piped water and electricity, with trains in tunnels and cars on elevated roadways, with fiber optics under the pavement and air-conditioning plants for buildings with windows that cannot be opened.

Our new urban centers have the vulnerability to terrorism and attack built right into them. Any modern city can be held hostage by a single Unabomber, brought to a halt by nineteen fanatical men, or devastated by any small raiding party drawing on modern scientific knowledge, from malicious computer programming to radioactive “dirty bombs” to infectious bacteriology. To understand the dangerous future of these WMDs, we’ll first take a quick look at their history.