The group is thought to now be stronger in numbers than at any point since they were ousted in 2001 - with up to 85,000 full time fighters, according to recent Nato estimates.
So less than half of the Afghan National Army's 180,000 troops:
https://en.wikipedia.org/wiki/Afghan_National_Army
There is a rule of thumb that attackers need to outnumber defenders 3 to 1 in order to win. But that assumes the defenders actually want to do their job.
"Soldiers in Ghurmach in the northern province of Faryab had spoken to a local media about the same topic just a month before, saying, "We haven't eaten for days. We only have four sacks of flour for 400 soldiers. No one cares about us. We can't fight the Taliban on only bread and water.""
It seems that endemic corruptions was one of the main reasons.
"[...] In May 2018, the police in Badghis province in the north-west of Afghanistan confirmed that a contractor that provided food to Afghan security forces was serving up dog meat. "
"[...] According to the same report, there are thousands of 'ghost soldiers' in the ranks of the Afghan army: soldiers who exist only on paper, allowing commanders to inflate their budgets and fill their pockets. An Afghan army soldier earns only 200 dollars a month. "
With all the money that was funneled from the coalition, this doesn't surprise me. In hindsight, I don't see how the Afghan government could have ever survived the Taliban without indefinite presence of the USA.
https://observers.france24.com/en/20200218-afghanistan-corru...
That is more of a rule for an individual battle. The Afghan army cannot mass all its troops for a battle. They have to attempt to hold large amounts of territory, spreading themselves thin. The Taliban can mass troops in specific areas, so it outnumbers the defenders, and then move on. It is not accurate or fair to portray the ANA as some sort of clearly superior force that just doesn’t feel like fighting.
At which point the army could not just move back in and retake the "lost" area because...?
Welcome to the last 20 years of counter insurgency in Afghanistan.
The Taliban did not roll through Afghanistan as a big wrecking ball. A moment of thought would tell you that this model does not match the growing area they controlled, nor the way it grew toward Kabul from all sides. Nor is it plausible that the army, with more than double the troops, better vehicles and air support would be unable to converge on your hypothetical wrecking ball.
The Taliban avoided big battles, because they always lost those. By all accounts, their final advance was so rapid only because they met virtually no resistance. When they reached Kabul, they initially stayed outside the city, until word got out that the military and police had abandoned their positions and looting was underway, at which point they announced that they were going in to restore order.
This stability gives a sizable level of local support. For many however it's literally a death sentence.
Taliban rule is incredibly oppressive though, almost cartoonishly so. I can't think of any contemporary regime more tyrannical and authoritarian. Their stated aim is to "recreate the time of the Prophet" 1400 years ago.
China isn't totalitarian but I believe the Taliban aims to be. I should look into this more.
Kim Dynasty, North Korea.
Support might be a strong word. More like acquiescence. The Taliban actively attempt to undermine and destroy security in areas it does not control. Most Afghans don’t like the Taliban but understand there isn’t really a viable alternative. It is either the chaos of no control, the Taliban randomly attacking people in places secured by the government, or the repressive security of the Taliban.