A month ago, one of Afghanistan's most famous warlords vowed to defend his city from the Taliban as he called for locals to join the fight.

Ismail Khan, 75, has for decades been a force in Herat, Afghanistan's third-biggest city that is of huge strategic value partly due to its close proximity to Iran.

But on Friday, after government forces had left the city and Taliban militants had taken control without a battle, the "Lion of Herat" was nowhere to be seen.

Hours after seizing the city, a group of insurgents pulled down an Afghan flag from a police station as cars and bicycles passed in seemingly normal traffic.

Others stood on the bonnet of a humvee vehicle that had been abandoned by the retreating government troops.

One insurgent gave the hint of a smile while looking into a camera, with a rocket-propelled grenade on his shoulder. 

The white flag of the Taliban waved through the air on a pole pegged to a motorcycle.

Like in other cities lost to the Taliban over the past week, authorities claimed they gave up to avoid bloodshed among civilians.

"We had to leave the city in order to prevent further destruction," a senior security source from Herat told AFP, adding that troops and city officials had retreated to army barracks outside of Herat.

Khan's vast militia had a series of successes against the Taliban when the hardline Islamic group first came to power.

But he was forced to flee to Iran with thousands of his men in 1995 after an ally defected to the insurgents.

He was captured by the Taliban in 1997 when he returned to organise an uprising, but escaped from prison two years later and was at large until the US invasion in 2001.

Last month he was again breathing defiance.

"We will soon go to the frontlines and with the help of God change the situation," Khan, 75, told a news conference.

"We hope that men and women of Herat decide at this moment to support the resistance front to defend their freedom and safeguard their honour," Khan said.

He blamed the government for the rapidly deteriorating situation and urged the military to show more backbone.

"We demand all the remaining security forces resist with courage."

What next for Afghanistan as Taliban rise again?
Afghanistan is on the precipice and the nation's security forces have all but collapsed after being battered by a Taliban offensive they were unable to halt.

To add to its woes, Washington has announced plans to evacuate its nationals in Kabul, a symbolic and shambolic end of the US presence after nearly two decades of conflict.

With the Taliban controlling the vast majority of the country's cities and rural areas, and Afghan security forces largely defeated, here follows some questions and answers that may help explain the current situation:

What's the Taliban's strategy?
The Taliban have never shied away from saying what they want -- the complete resurrection of their Islamic emirate that ruled from 1996 - 2001.

A lot of analysis and head-scratching was devoted to how exactly they would achieve their goal -- through talks, brute force, or a mixture of both.

In the end, their military strategy proved sufficient: overwhelm government forces with multi-pronged attacks on targets throughout the country.

To do that they first had to get American boots off the ground -- which they did by securing a deal with war-weary Washington and pledging not to hit US targets in exchange for their withdrawal.

Part of the deal also meant Washington pressuring the Afghan government into releasing thousands of Taliban prisoners -- most of whom immediately rejoined the fray.

With such breathtaking successes in the last eight days the Taliban may now have the confidence to offer the government the chance of unconditional surrender.

If Kabul baulks, expect the Taliban to push for the capital with force.

What happened to the Afghan military?
No doubt books will be published and lectures given for years, if not decades, on this subject -- what exactly went wrong with the Afghan security forces?

Corruption, the lack of a will to fight, and the vacuum created by the US exit likely all played a part in the Afghan military's ultimate demise.

For years, the US government issued reports detailing the vast amounts of corruption within the Afghan security forces.

Commanders routinely pocketed money meant for their troops, sold weapons on the black market, and lied about the number of soldiers in their ranks.

The Afghan forces were also entirely dependent on US air power -- from logistics to strikes, along with maintenance.

And to make matters all the worse, the security forces never had much in the way of effective leadership.

They were micromanaged by civilians in the presidential palace with little military experience, or ignored by ageing generals who appeared more involved in petty political fights than the larger war at hand.

The US-trained commando units were the hope, but in the end they were not enough to shoulder the entire fight.

How does it end?
The Taliban have the upper hand across the board.

The government now controls just three major cities, and is unlikely to have the logistical manpower left to marshal a successful defence of the capital. 

The Taliban are moving rapidly towards Kabul with reports suggesting their fighters are making progress on the northern and southern flanks of the capital.

The US and international community are most likely piling pressure on the Taliban and Afghan government to reach some kind of deal.

But the Taliban ultimately hold all the cards.