The Afghans simply want to know who will be in charge

For me, the leaked American cable traffic on Afghanistan contains few surprises. The cables show a great global foreign service doing its job: reporting, dutifully and sometimes at greater length than strictly necessary, what was happening and what it was hearing. Truths inconvenient for the power in Washington – about US allies and associates in the Afghan enterprise – are told.

As ambassador in Kabul from 2007 to 2009 I knew, and reported to ministers in London, that President Hamid Karzai was suspicious of British efforts and motives in Helmand. On that, as on so many other issues, Karzai is the authentic voice of many of his people. No secret there. I also reported American concerns about the level of military resources Britain was devoting to the vast task of stabilising Afghanistan's most dangerous province. No secret there either.

We knew too that the Americans in general, and the US marines in particular, believed they could do a better job in Helmand than British forces: in their view it was a matter of attitude as well as of resources. Competition between allied armies in war is neither unusual nor necessarily unwelcome (though we couldn't help noticing how criticism of the British effort subsided once the Americans came to see for themselves just how tough the challenges in Helmand really were).

The real tragedy about these telegrams is that they miss the point: that the entire western military effort in Afghanistan will in the end be for nothing unless it is part of a wider political strategy. Such a strategy should bring together all the internal parties – not just the Taliban – to a decades-old conflict, and systematically engage Afghanistan's neighbours in gradually stabilising the country, from which the whole of south-west Asia would benefit.

In that broader strategic perspective, debating troop levels in Helmand is a bit like arguing over how much aspirin to give a cancer patient. Garrisoning the town of Sangin more efficiently may produce more relief from pain (or violence). But without action to treat the underlying disease (which is political, not military), such relief can be only local, and temporary.

The long-suffering people of Helmand know this well. What they really want is not more schools and clinics, or roads and irrigation ditches (although all of those would be welcome), but to know who will be in charge of their village or valley five months or five years from now. They will back the probable winner. But, in the absence of a political solution, the fatal flaw in our whole counter-insurgency "strategy" is that for the average Pashtun peasant farmer, caught between the Taliban and the narco-mafia, the Afghan government is not necessarily the long-term winner.

As ambassador, I was guarded day and night by a close protection team founded by the Royal Military Police. Many of the 20-year-old corporals who protected me had come to Kabul from tours in Helmand. If I ever need a definition of sheer courage, it is those young RMPs accompanying the Afghan police on patrol through the fields and tracks of Helmand's "green zone", as the province's fertile central area is known. But all their work will have been wasted if the politicians and diplomats, in Washington at least as much as Kabul, do not deliver the political approach essential for stabilising Afghanistan.

The leaked cables refer to a visit that Joe Biden, then America's vice-president elect, paid to Helmand in January 2009, just before the inauguration. At the time I had an exchange with him, over lunch with the US marines. Like many American politicians meeting a Brit, the senator felt the need to quote Churchill, mentioning – apropos of nothing obvious – his view that democracy was the worst form of government – except for all the others. My response was to remind Biden that Churchill had also observed that one could rely on America to do the right thing – once it had exhausted all the alternatives.

For the sake of our soldiers, so many of whom have fought and died or been wounded in Helmand – and above all for the sake of the countless Afghans, in and out of uniform, who have been killed and injured in this conflict, and for whom there is no Selly Oak hospital or Walter Reed army medical centre – I have a devout hope: that president Obama and his national security team show in this month's policy review the courage of their original conviction; and that, in the end, the problems of Helmand, of Afghanistan and of the region are political, not military.

Drawing on our history, our political and diplomatic expertise, and the huge sacrifice of blood and treasure we have made in Afghanistan, Britain's role should be to help give the Obama administration the confidence and the courage it needs to do that right thing. As Obama's Democratic predecessor might have said: "Afghanistan: it's the politics, stupid."

Sherard Cowper-Coles, Britain's former special envoy to Afghanistan and Pakistan.