The National Bureau of Economic Research just published a report on the effect of civilian casualties in Afghanistan and Iraq that confirmed what critics of our foreign policy have been saying for years: the killing of civilians, although unintentional, angers other civilians and prompts them to seek revenge.

This should be self-evident.

The CIA has long acknowledged and analyzed the concept of blowback in our foreign policy. It still amazes me that so many think attacks against our soldiers occupying hostile foreign lands are motivated by hatred toward our system of government at home or by the religion of the attackers.

In fact, most of the anger towards us is rooted in reactions towards seeing their mothers, fathers, sisters, brothers and other loved ones being killed by a foreign army. No matter our intentions, the violence of our militarism in foreign lands causes those residents to seek revenge if innocents are killed.

One does not have to be Muslim to react this way.

Our battle in Afghanistan resembles the battle against the many-headed Hydra monster in Greek mythology. According to Gen. Stanley McChrystal’s socalled insurgent math, for every insurgent killed, 10 more insurgents are created by the collateral damage to civilians.

Every coalition attack leads to six retaliatory attacks against our troops within the following six weeks, according to the NBER report. These retaliatory attacks must then be acted on by our troops, leading to still more attacks, and so it goes.

Violence begets more violence. Eventually, more Afghanis will view American troops with hostility and seek revenge for the death of a loved one. Meanwhile, we are bleeding ourselves dry, militarily and economically.

Some say if we leave, the Taliban will be strengthened. However, those who make that claim ignore the numerous ways our interventionist foreign policy has strengthened groups like the Taliban over the years.

I’ve already pointed out how we serve as excellent recruiters for them by killing civilians. Last week, I pointed out how our foreign aid, to Pakistan specifically, makes it into Taliban coffers.

And, of course, we provided the Taliban aid and resources in the 1980s, when they were our strategic allies against the Soviets.

For example, our CIA supplied them Stinger missiles to use against the Soviets, which are strikingly similar to the ones now allegedly used against us on the same battlefield, according to those Wikileaks documents.

Our friends have a funny way of turning against us. Manuel Noriega and Saddam Hussein are also prime examples. But Congress never seems to acknowledge the blowback from our interventionism.

We have done enough to the Afghan people and to ourselves. It’s time to leave.

Ron Paul represents the 14th Congressional district of Texas.