B-52 Stratofortress bombers are old now - the US stopped building them about 1963, but there has been much updating and modification. They can now carry cruise missiles and "smart bombs", not just the original "iron" or "dumb" free-fall bombs.
Apart from their enormous destructive power, their use against Taliban frontlines is an indication that Taliban tactics is making things difficult for the Americans.
Dispersal into populated centres have made the Taliban hard to hit without causing civilian casualties. One can accept the US claim of "not targeting civilians". This is not just because of undesirable political repercussions.
It was not their form in the second World War: they accepted the aircrew casualties involved in daylight bombing, partly for its better accuracy and partly to reduce civilian casualties (see Noble Frankland's account of the October 1943 attack on Schweinfurt and consequent development of the Mustang escort fighter).
Some of the smart bombs have been diverted from their targets by the smoke of previous bombings, etc. This can break the laser lock on a ground target and cause bombs to miss. Smart bombs have been over-hyped, not deliberately misused.
However, old-fashioned "carpet bombing" with "iron" bombs proved devastating to Iraqi troops, well dug-in in 1990/1991. Their excellent field engineers had learnt well from the Russians.
But once US air supremacy was established, the defence work was nullified. The target area was comparatively small and concentrated in open desert. There was no foliage; the trenches were visible from above and relatively easy to hit.
Fuel-air bombs caused many casualties - the oxygen was burnt out of the air. It was reckoned that three B-52 bombers, flying in formation seven miles up, could "carpet bomb" an area 11/2 miles long by a mile wide with 153 bombs (750 lb each). In last Wednesday's carpet bombing single aircraft were used.
Outside populated areas, the Taliban are in rocks and caves. Some caves are natural, others were natural but were extended and improved during the Russian and other wars.
Much work has been done on deep penetration bombs. Delayed detonation as well as accuracy are needed . The bomb must be able to penetrate thick rock, possibly, to reach an enemy headquarters, and very good intelligence is required on the location of targets.
Some of this work concentrated on buildings. It was required to penetrate multi-storey buildings and get right down to basement HQs before detonation.
Bombs were produced which could count the "voids" as they went down through floor after floor and detonate at a particular floor level or in the basement. One has not seen much about them recently, but that does not mean that they have been a failure or abandoned. The number and variety of specialised bombs and warheads now available are a sobering manifestation of human ingenuity.
Strike aircraft followed the carpet bombing. These have been operating from 15,000 ft. The Taliban broke cover afterwards.