ALLIED planes pounded the concrete fort for weeks. First they used 250-pound bombs. Then they dropped heavier ordnance, mixing in artillery fire for good measure. Finally, on Oct. 8, 1944, US B-26s delivered a final blow: Thirty-three 2,000-pound bombs, 10 of which were direct hits or near misses.
Fort Saint Blaise, near Metz, France, sustained heavy damage, with holes blown in some bunker roofs and a gun emplacement destroyed. But many German troops survived and kept fighting. After the war, the United States Strategic Bombing Survey noted that while the bastion was under constant artillery and air attack, the bombardment ``neither individually nor collectively caused enough damage to neutralize the fort.''
Small bombs did no material harm; 2,000-pound bombs could penetrate walls, but even then ``too great an area of damage cannot be expected,'' concluded the survey.
Basic lesson stands
Air power has much advanced since World War II. But the basic lesson of Fort Saint Blaise still applies: Knocking out single targets with bombs can require a tremendous amount of military effort, particularly if the target is ``hard,'' or armored against attack.
Thus the difficulty of destroying Iraq's Republican Guards and front-line troops from the air, despite the thousands of allied air sorties already run against them.
Consider Iraqi tanks, which are largely dug in and surrounded by earthen berms. ``It pretty much takes a direct hit'' to destroy protected armor, noted US Army Lt. Gen. Thomas Kelly in a Pentagon briefing last week.
Video footage of laser-guided bombs blowing up buildings and bridges in a single bound has perhaps led the public to believe that bombing is a less messy business than it really is.
But not all, or even most, of the tonnage delivered so far by allied forces has consisted of modern, guided equipment. Those weapons are reserved for targets that require precision. Many bombs dropped are so-called ``iron'' bombs, which just fall free. And precision bombs, of course, don't always hit the target.
US Central Command's own figures show how bombardment is more of a slow, grinding process than one of quick and massive destruction. In the first two weeks of the war, allied planes targeted 33 bridges. They ran 790 aircraft sorties, according to Central Command. Roughly half of those represented actual bombing runs - meaning around 12 combat aircraft were sent against each bridge.
Using similar calculations, approximately 14 bombing runs were made against each of 29 air defense targets in the war's first weeks.
Each of 31 sites suspected of involvement in working on nuclear, biological, or chemical weapons received the attention of eight bombing runs.
The scale of a bombing raid can be seen in the details of a British operation against an ammunition dump in Iraq last week, which was targeted by at least 40 1,000-pound bombs.
Secondary blasts likely
Such targets as ammunition dumps and fuel collection points have potential for what military planners call ``secondary explosions'' from their own stocks. ``They really are vast, and require anything but precision bombing,'' noted a British military officer in Saudi Arabia.
The most destructive bombs being used by coalition forces are I-2000s. They have 2,000-pound warheads with strengthened casings for special concrete penetration ability.
These bombs, equipped with laser guiding equipment, are the ones seen in film clips flying down air shafts and shattering hardened aircraft bunkers after being dropped by F-117 or F/B-111 aircraft.
The power of a 2,000-pound bomb (typically, only 1,000 pounds of this weight is explosive) can be gauged by the fact that one could probably destroy a hardened concrete aircraft shelter even if it landed on the shelter's roof, rather than going inside, says an experienced weapons analyst who works on Pentagon contracts.
A 500-pound bomb wouldn't have the same effect. Neither would a cruise missile, which typically carries a 1,000-pound warhead.
Dropped into a building, a 2,000-pound bomb would destroy rooms for ``tens of feet,'' says the weapons analyst, who requested that his name and his firm's name not be revealed. Dropped into an open factory, it would damage heavy machinery ``for 100 feet.''
But if targeted on prepared troops, a 2,000-pound bomb wouldn't have much effect on anything or anyone dug into the earth as close as 50 or 100 feet from the point of impact.
``Most of the force would go over your head,'' says the analyst. ``That's why you dig foxholes.''
Thus Iraqi Republican Guards and other troop formations are in a way more frustrating targets than buildings or bridges.
The analogy some experts use is to a shooting gallery: At first glance, there look to be lots of targets. But close your eyes and shoot, and chances are you'll miss. The percentage of open space to target is much greater than it appears.
Tanks hardest targets
Tanks in prepared positions are perhaps the hardest targets of all.
One munition that B-52s bombing armor formations are likely using is the antitank Rockeye cluster bomb, which breaks apart like a shotgun shell and saturates an acre with 2-pound bomblets.
Each bomblet contains a small, shaped-charge explosive designed to shoot a thin, concentrated bolt of explosive energy through steel and peel fragments off the inside of the armor itself.
Pool journalists in Saudi Arabia have also reported the presence of fuel-air explosives at one air base. Fuel-air bombs work by spraying a mist of explosive into the air, then igniting it. They create tremendous blast waves, and were used in Vietnam for clearing helicopter landing zones. They are sometimes touted as the closet conventional analogy to nuclear weapons.
Fuel-air bombs might be used against Iraqi armored formations, or as mine-clearing explosives. ``They've always had a terrific press, but nobody's every really managed to make them work,'' says Norm Friedman, an author of weapons systems reference books.