When Taliban forces swept into the Musa Qala district of northern Helmand last week it was a moment rich in symbolism for their fighters. Eight years ago this was a British battleground where 23 British soldiers lost their lives and the name passed into the history of the operations in Helmand. The move was not unexpected as the Taliban had already occupied the nearby towns of Sangin, Nowzad and Kajaki but the loss of Musa Qala was “the big one” simply because it is such an iconic name.

It also gave notice that Taliban commanders now feel able to move at will in Helmand province and that the fledgling Afghan security forces lack the capacity to oppose them I the open field. More than any other factor that change in the strategic situation has sent alarm bells ringing in the minds of former British army officers with experience of the long war against the Taliban in Afghanistan. With the last of Nato’s 12,000-strong garrison due to be withdrawn next year Colonel Richard Kemp, a former British commander in Afghanistan warned that the country could once again become “a safe-haven for terrorism launched against the West.”

Drawing comparisons with what happened in Iraq following the withdrawal of US forces from the country Kemp also warned that Afghanistan could be similarly harmed if the west failed to continue supporting the democratically elected government led by Ashraf Ghani who became president a year ago. Although most western forces have now been withdrawn a large training establishment remains and while Kemp acknowledged that it is a “huge commitment” worse would follow if it were cut back: “So I think it’s important that not only US but other Nato forces put a significant effort in to assisting the Afghan government for as long as is needed.”

Kemp’s fears should not be minimised as last week’s operations in Musa Qala showed that the Afghan security forces were unable to contain the Taliban’s encirclement tactics and that not even the use of US air strikes was able to turn the tide. During the fighting it was reported that 70 Afghan soldiers were killed, a figure that will be unsustainable if the fighting continues over several months. Advances of that kind also give heart to Taliban commanders. Not only do they provide evidence that the their units on the ground are capable of overcoming Nato-trained government forces but they pass the initiative back to the Taliban in the attempts to find a negotiated settlement and make a resumption of talks less likely.

Unfortunately it is not just in Helmand where the Taliban has been gaining ground. The present insurgency has also been successful in the north of the country where the Taliban threat has been compounded by the arrival of jihadi fighters from the Islamic Movement of Uzbekistan (IMU). This warlike grouping was finally defeated by a Pakistani military offensive last year and forced to leave its redoubts in the North Waziristan tribal area on the Afghan border. At the same time IMU’s leadership broke ranks with the Taliban chain of command and switched allegiance to Daesh's leader Abu Bakr al-Baghdadi.

There is now the added danger that other younger Taliban fighters in Afghanistan will become dissatisfied the slow rate of progress – despite last week’s success in Helmand – and will start turning to Daesh. Evidence has already surfaced of Daesh activity in the northern province of Kunduz which was the responsibility of the German Army during Nato’s operations.

This trend has become more worrying since the death of Mullah Omar and the emergence of his successor Mullah Akhtar Mansour who is distrusted by many of the Pakistani Taliban. Senior Pakistani security forces commanders are claiming as many as 300 Taliban commanders could already have switched allegiance to Daesh. According to Michael Kugelman, Afghanistan expert at the Washington-based think tank Woodrow Wilson International Centre for Scholars, the extremist group is “flavour of the month right now. It has a dramatic appeal to a lot of alienated militants.” However, he also cautioned that the Taliban in both Afghanistan and Pakistan remained “a formidable fighting force” and that its reputation will have been enhanced by last week’s success at Musa Qala.