The pilotless, missile-armed “Reaper” is operated from ground-control stations thousands of kilometers away.

LENS

Our earliest ancestors had to look into the eyes of their enemies before clubbing them to death in the brutal territorial disputes on the savannah. Until, that is, some forward-thinking primeval strategist concluded that he could hurl rocks from the high ground.

And ever since, war - whether fought with arrows, guns, artillery or airplanes - has grown steadily more distant and impersonal. That has never been more true than in our own age of robotics, satellite communications and surgicalstrike missiles.

Yet as acts of war have become remote, and seemingly less risky, evidence is accumulating that there are unanticipated consequences for the perpetrators of war from afar.

Take today’s pilotless drone aircraft, operated from command posts half a world away on United States soil. The drones hover unseen over Iraq, Afghanistan and Pakistan, keeping targets under video surveillance until commanded to fire.

The Times’s Mark Mazzetti wrote that American commanders believe drones have severely weakened Al Qaeda’s leadership in Pakistan without risking a single American soldier.

But it is not that simple.

Some experts, Mr.Mazzetti reported, now fear that drone warfare could “promote the psychology of anti-American militancy that is metastasizing” in the region.

Moreover, P.W.Singer, an expert on robot warfare, told Mr.Mazzetti that in the Muslim world the use of drones is viewed as a sign of cowardice .

“If courage is the coin of the realm, then courage is what proves to the local Pashtun tribes that you are their allies,’’he said.

Then there is the fallout; the drone attacks can provoke rage on the ground. Even “surgical’’ strikes often kill innocents, Mr.Mazetti wrote, and when this happens the survivors seek revenge.

In another article, Mr.Singer, who is the author of the book“Wired for War,”told the Times reporter Christopher Drew that when combatants on one side are so detached from the carnage of battle, there is a risk of commanders’becoming“more cavalier’’about the force they use.

But even when combat is conducted from the safety of Nevada or Arizona, it can take a psychological toll. Air Force officials told Mr.Drew that some drone operators avoided watching missile strikes on video. When they finish their day’s work, it “can be hard to transition from being a computer-screen warrior to dinner at home or their children’s soccer games,’’Mr.Drew wrote.

Warriors of the future may be not burdened with any emotions. The Times’s Cornelia Dean wrote that machines made for ground combat could be programmed not just for killing but also for ethical decisions. Unclouded by revenge or fear, a robot soldier would be unable to violate the Geneva Convention, some scientists theorize.

But even if“ethical’’or“surgical,’’can warfare ever truly be detached from its brutish beginnings?

As Albert Einstein once said:“I don’t know what kind of weapons will be used in the third world war, assuming there will be a third world war. But I can tell you what the fourth world war will be fought with - stone clubs.”