Mullah Omar is the Lazarus of the international jihad. The one-eyed Taliban leader has been pronounced dead at regular intervals over the years, with each occasion prompting furious denials from Taliban officials and, in due course, a missive purporting to be from the man himself.

But this time is different. The Afghan president's office has released a statement saying that Omar died in April 2013. Other Afghan officials have attributed the claim of Mullah Omar's death to their counterparts in Pakistan, where Omar is widely believed to have been under the protection of that country's intelligence services.

What is significant is the timing, for the Taliban faces an internal power struggle, in part over budding Pakistan-brokered peace talks with the Afghan Government, and due to the growing challenge from ISIS in Afghanistan.

In many ways, the Taliban has been fragmenting for years. The authority and legitimacy of older Taliban leaders, who established themselves in the 1990s, has waned. The US-led kill-capture campaign against mid-level commanders gave rise to what one study called a generation of 'more ideologically motivated and less nationalistic...and therefore less pragmatic' leaders with little memory of an Afghanistan at peace and less inclined to compromise with Afghan Government. More recently there have been several reported power struggles at the top, pitting senior leader Mullah Akhtar Mansoor, who has supported peace talks, against various figures said to oppose them, including Mullah Omar's 26-year-old son Mullah Yaqub and sacked military commander Abdul Qayum Zakir.

It is those talks, which began in the Pakistani town of Murree on 7 July and were scheduled to continue on 31 July, which would be most immediately affected were the news of Omar's death to be confirmed and acknowledged.

In 2012, former State Department adviser Vali Nasr told the New Yorker's Steve Coll that Omar was crucial because 'there is no legitimacy to a Taliban decision without him. He is the Ho Chi Minh of the war. If you have him, if you hold him, you control the whole organization'. While this may exaggerate the degree to which the Taliban obeys a formal hierarchy, perceptions of Omar as a moral arbiter – especially in his role as 'commander of the faithful' – is crucial.

This is why, on 15 July, Mullah Omar 'endorsed' the peace talks in a supposed Eid message, smoothing over an argument between the Taliban's Qatar office and its leaders in Pakistan. Dead or alive (one senior Taliban figure openly acknowledged that Omar had 'no control' over the message), Omar's perceived imprimatur for the talks and for specific envoys has given the process a degree of coherence and credibility. It has encouraged the hope, however modest, that what might be agreed in Pakistani hotels could, eventually, translate into changes on the ground in Afghanistan. Even with Omar deemed alive, it was far from clear what proportion of Taliban commanders and fighters would abide by any settlement. But acknowledging his death would challenge the legitimacy of those who claim to speak on their leader's behalf. Indeed, those dissatisfied with the course of events may have leaked the news precisely for this reason.

Even if those in favour of talks can ride out the consequences of this news and sustain the dialogue with Kabul, they could see increasing dissent, and even defection, from their commanders in the field. ISIS has increasingly sought to challenge the Taliban's authority in the south and east, hoping to co-opt disgruntled Taliban commanders. ISIS's presence remains limited, and its Afghan leader was killed in a drone strike earlier this month. ISIS faces a radically different sectarian and political environment to that in Syria or Iraq, and has made few inroads so far. But the group would exploit any chaos in the Taliban ranks.

For the past fourteen years, Mullah Omar has been an unseen, ghostly presence over the war in Afghanistan. It is the idea – the myth – of Omar, rather than his everyday leadership, that matters. Formal acknowledgment of his loss could change the direction of this long war. The irony is that the West might come to regret the splintering of a group they fought for over a decade, both for its impact on peace talks and for the opportunities it has created for new and more radical actors like ISIS.

Photo by Flickr user thierry ehrmann.