As Oelrich, of the Federation of American Scientists, noted, "Now the problem is, How do we know the target is in one building versus another?"
The number of civilian deaths caused by U.S.-led bombing campaigns in recent conflicts have been reduced due to the use of precision-guided weapons and changed tactics.
But the toll in human lives remains.
Civilian death tolls during wartime can be difficult to tally. The Pentagon does not estimate civilian casualties.
University of New Hampshire professor Marc Herold has attempted to catalog civilian bombing deaths from the late 2001 aerial campaign in Afghanistan.
Herold compiles casualty reports from media sources. Debate rages over exactly which agencies and reporters constitute "credible" sources and also over information about the precise causes of death in war zones where many combatants are not even in uniform.
"Unfortunately, in all this discussion of precision weapons, the focus has been 'We only kill the bad guys,'" Herold said. "I think there's a real effort at conveying a certain perception of what these weapons do. When in fact it's not at all clear that they [perform so efficiently]."
"When you drop very powerful bombs in civilian-rich areas, given the probability of bombs missing by only 10 meters [33 feet] or so, you're going to wipe out a lot of people," he continued. The question of just which people are killed by bombing can become blurred during the type of insurgency conflict now unfolding in Iraq.
Pike, of GlobalSecurity.org, said targeted bombing in Iraq today can keep insurgent groups from concentrating.
"We can't prevent them from setting off roadside bombs from 28,000 feet [8,500 meters]," Pike said. "But if they ever get together in military-sized units [the U.S. Air Force] will blow them up, and I think that's reflected in the continued use of air strikes over there."
The effectiveness of those continued air attacks is challenged as insurgents adapt their tactics.
"Our opponents go out of their way to change their operations [and] make it harder for us to get [intelligence] information," said Biddle, the U.S. Army War College professor. "They do a better job of concealment, of dispersing, of reducing their radio and other transmissions. The heart of guerilla tactics is denying information on where you are or even who you are."
He noted that al Qaeda operatives in Afghanistan have become particularly effective at such evasions and that Iraqi insurgents have also adapted.
Oelrich, the FAS strategic weapons analyst, said, "A downside is that we are sometimes so cautious about exposing our own forces to harm that, based on a tip or some intelligence, we determine that bad guys are in a house, and we blow it up with a precision-guided bomb."
Such actions have led to some notable mistakes.
Oelrich continued: "Because we have these weapons, we can [use them] to take the easy way out rather than put guys on the ground with eyes and ears who can see the real situation."
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