[D]uring the peak six years of the Vietnam war, 6.7 million tons of bombs were dropped. That was the same rate they were dropped during the major bombing campaigns of World War II. But in eight years of fighting in Afghanistan and Iraq, only 42,000 tons have been dropped. Thus, while in the past, a million tons were dropped a year, for the war on terror, less than 6,000 tons a year were dropped. That means a reduction of over 99 percent. Even when you adjust for the different number of U.S. troops involved, that's still over 97 percent fewer bombs dropped. . . .
[D]uring Vietnam the average bomb size was close to 1,000 pounds, now it's less than half that. Weapons like the hundred pound Hellfire missile are more popular with the ground troops, than the 2,000 pound bomb that was so often used in Vietnam.
Most of the bombing is now being done in Afghanistan. In Iraq, less than a ton of bombs a month are being dropped. In Afghanistan, it's over 100 tons a month. In Afghanistan, this tonnage has declined nearly 40 percent in the last year. Partly due to the greater use of smaller bombs and missiles, and partly due to the greater use of civilians as human shields by the Taliban. . . . About a hundred civilians are killed each month in Afghanistan. Most are killed by the Taliban, but 10-20 percent are killed by American smart bombs, missiles and shells.
A single U.S. fighter aircraft can carry enough ordinance for several months worth of bombing in Iraq. A month of bombs in Afghanistan can be carried on about ten A-10 fighters, or five B-52s. Greater accuracy from guided ammunition also means that U.S. aircraft carrying them don't have to get as close to the targets (which makes them vulnerable to anti-aircraft fire) as was previously the case.
Once can certainly argue that Afghanistan and Iraq are not the sort of "near peer" conflicts that should be the basis of military procurement. But, there is also overwhelming data that guided munitions do mean that far more military objectives can be secured with far, far fewer aircraft. This suggests that it may be time to downsize the Air Force.
This also changes the game when it comes to proliferation of military weapons. Many military forces and insurgent forces which would be unable to afford state of the art military aircraft (which cost up to $200 million each), can afford a small number of bottom of the line military aircraft outfitted with state of the art guided munitions. While these compromise aircraft wouldn't measure up in air to air combat against modern forces, they could dramatically change the impact that air to ground warfare has on ground combat, even in quite small numbers. This could tip the balance of power in a proxy war or counterinsurgency somewhere in the developing world or the Third World. Ten million dollars used to buy half a dozen crop dusters or Cessna aircraft, and a hundred guided bombs could turn an otherwise rag tag militia or insurgent force into a terrifying terror threat to large population centers.
A large share of U.S. casualties in Iraq have been caused by improvised explosive devices, frequently triggered via cellphone by a distant observer who can see U.S. forces approach the bomb's hidden location (e.g. through binoculars). Basic consumer electronics wedded even crudely to ordinance can produce surprisingly sophisticated weapons.
This is also a trend which could continue even further. Guided missiles that are a fraction the size of the hundred pound Hellfire missiles (as little as five pounds), and guided artillery shells, are entering or on the verge of entering widespread use in the battlefield. In situations with reasonably good tactical intelligence on the ground, and an absence of heavy military opponents (e.g. armored personnel carriers, tanks and ships), small narrowly targeted ordinance delivered to their general destination by drones may become the norm.
One can easily imagine guided munitions with grenade or large caliber bullet sized warheads, and improved microelectronics could keep the guidance systems for that kind of munition proportionately small. Since scale is important in aerodynamics, it is much easier to make small packages fly manueverably than it is to do so for large packages.
We may not yet have reached the era of Frank Herbert's Dune series where artificial intelligence guided micromissiles were used as weapons of personal assassination, but we are closer to that technological extreme than one might think. Bird sized drone aircraft are already in use militarily. These aircraft have stealth, not because they have artificially small radar images, but because they really are similar in size to the bats and birds that fill peaceable skies and operate in the same airspace. Grenades that explode in a certain mode at a certain pre-programed location on the line of fire are entering production. Advanced digital optics and GPS based forward observer gear make it possible to be very specific about where ordinance lands and what will be there when it hits, even when ordinary vision is obscured or there is no convenient spot to observe from close at hand.
Increasingly, modern military technology makes knowing where to point munitions a key limiting factor relative to the ability to deliver the right amount of ordinance to the right place in a timely manner, and even that barrier is easing.
I've always been a bit skeptical of the Mutual Assured Destruction theory behind restrained use of nuclear weapons (i.e. zero since the two bombs dropped by the U.S. at the end of World War II). Equally important has been the fact that flattening a medium sized city in a single blow is rarely militarily useful. The military problem of the 21st century has been that 100 pound Hellfire missiles are too large to be sufficiently discriminating, so it is little wonder that nuclear bombs haven't been the right solution to the military's problems.
While nuclear wastelands are a worry, war via unmanned assassination devices may be an equally plausible distopian future.