This weeks’ EXPLAINER is former BBC Kabul correspondent, Dawood Azami, explaining why in Afghanistan this summer the Taliban is mounting its biggest offensive since the US-led invasion in 2001. Audio available in Content Depot

The Taliban and the Summer of 2014

While all eyes are on the Islamic State in Iraq and Syria, what is the Taliban up to Afghanistan? The answer: its biggest summer offensive in the country since the US-led invasion in 2001.

The BBC’s former Kabul correspondent, Dawood Azami, explains:

Operation in Zari District

In the middle of August, Taliban fighters captured a district in Afghanistan’s eastern Nooristan province.

This is the latest victory for the Taliban in their fighting this summer which is the toughest since the US led invasion of Afghanistan thirteen years ago.

Over the past two months, the Taliban has been mounting increasingly intensive attacks across several provinces, often involving hundreds of fighters.

The Taliban aim is to expand its control and hold ground. This is a shift from the hit-and-run strikes using gunmen, explosives and suicide bombers.

The militants have focused on gaining strategic parts of the country, like border crossings and highways.

It is exploiting the vacuum left by the gradual withdrawal of foreign forces from Afghanistan. The US-led NATO combat forces are scheduled to leave the country by the end of this year.

In many parts of Afghanistan, the government’s security forces are overstretched and Afghan soldiers regularly complain about their weapons, which they don’t think are much good, and the lack of support they feel they are getting.

Both Ashraf Ghani (left) and Abullah Abdullah are still fighting for power in Afghanistan.

Uncertainty in Kabul over the outcome of this year’s presidential election (aimed at choosing a successor to President Hamid Karzai) has added to the vulnerability the security forces feel. Two months have passed since the run-off round in that election was held, but a winner has yet to emerge due to accusations of fraud. Both sides are claiming victory.

So there’s something of a vacuum. And the Taliban has stepped into it.

A caveat: the insurgents have managed to capture territory in several provinces. But their successes are limited thus far. They have not yet captured an entire province, and the government claims strategic assets remain broadly under its control.

Many Afghan civilians are injured and killed as a result of roadside bombs laid by the Taliban.

Afghan officials continue to accuse Pakistan’s powerful intelligence agency of supporting the Taliban and providing them sanctuaries on its territory. But these suggestions have been repeatedly denied by the Pakistani government, as has happened so often before.

Afghanistan does not have a functioning air force, and the Afghan security forces are still dependent on NATO air power.

In the absence of a fully equipped and capable military, complete with effective air power, the withdrawal of foreign troops poses a serious challenge to the stability of a country the US and its allies have spent so long trying to stabilise.

As foreign forces pull out of the country, this summer is the biggest test of Afghanistan’s own military strength.