The ironical end of the war
There is a great irony in the collapse of USbacked Afghan forces and the success of the Taliban. While the US officially focused on pulling US troops out of Afghanistan, what we really pulled out was the air power that supported not only US troops, but more importantly also Afghan soldiers.
The irony is that the US Air Force hated the Afghan campaign because the war lacked the kind of targets the US Air Force was designed to strike.
The United States has the most sophisticated and highest tech air force in the world, bar none. The F-22 and F-35, the two flagship fighter bomber and air superiority aircraft, lead the world in stealth and overall capability.
Yet it was the 1970s vintage A-10 and the 1960s vintage B-52 that proved most valuable in Afghanistan, the first because it is a hurtful, close support machine and the other because, in uncontested airspace, it can drop tons of bombs on the enemy - 70,000 pounds or 32,000 kilograms or 35 tons. The US also used the B-1 bomber, known as the Bone (vintage 1986), to good effect. But the B-1 is mostly grounded because the plane's airframes are cracking and some of its systems, including fuel pumps, have become leaky and dangerous.
Back in February the Air Force started to retire the B1s to make way for the forthcoming B-21, which doesn't fly yet. The key advantage of the B-1 is speed - if it is lurking in an area it can reach a target flying at Mach 1.2 (921mph or 1,482kph), while the B-52 lumbers along at a maximum speed of 400 mph (644 kph). When you need help in a hurry, the B-1 is more efficient than both the B52 and A-10.
When President Biden announced the US withdrawal from Afghanistan last April, the US began ending US airpower support. Unlike conventional wars, airpower in Afghanistan could only fill a singular role, which was bailing out US, coalition and Afghan forces in firefights with the Taliban - and also when possible, striking Islamic terrorists. Neither the F-22 or F-35 were useful in Afghanistan, and while US F-16s did fly, they were mostly providing ISR (intelligence, surveillance, target acquisition and reconnaissance) support.
As Colonel Jon C Wilkinson and Andrew Hill point out in their exceptional article, Airpower Against the Taliban in Air and Space Power Journal, the US Air Force's main focus is on high-end peer and near-peer adversaries and it specializes in air dominance and destroying ground targets.
In Afghanistan, there is no infrastructure belonging to the Taliban to destroy and the Taliban is not a near-peer adversary in the conventional military sense of the term. The Taliban, instead, is an insurgency with considerable popular support in the country, and what they lack in popular support they earn through fear, intimidation and viciousness. What US and allied airpower did in Afghanistan was to support coalition troops in firefights.
When the US pulled airpower back, the remaining Afghan forces were left with only the airpower the US left them. Most of that was a motley collection of propeller-driven fixed-wing aircraft and transport helicopters. The best of the lot were 19 A-29 Super Tucanos, designed as a COIN (counter-insurgency) aircraft. The A-29 is a turboprop aircraft developed in Brazil. The US also supplied Cessna 208B propeller aircraft, based on a commercial design.
Even with the equipment provided to the Afghan Air Force, essential contractor support all but disappeared starting in July. To add to the Afghan woes, at least one of their top pilots was murdered in front of his home, and all the remaining pilots were directly threatened by the Taliban, who knew who they were and where their families lived.
The US was never willing to provide powerful jet fighters or helicopter gunships to the Afghans.