It required some blunt speaking on the part of the military professionals, many of whom have spent years trying to get the Afghan campaign moving in the right direction, to inject a sense of realism – and a degree of optimism. Their argument was that while the war might be costly, both in terms of the blood and treasure so far expended, and present enormous challenges, there are encouraging signs that it is finally moving in the right direction.  The alliance now has a clearly formulated and effective strategy for ending the conflict and rebuilding the country after nearly three decades of strife. It also enjoys the added bonus of having sufficient resources to get the job done, with the arrival of thousands more American combat troops. Progress might be painfully slow, as my colleague Mary Riddell wrote earlier this week. But the unremitting military pressure that is being applied against the Taliban, together with the prospect of genuine political reconciliation among the country's warring parties, does hold out the very real prospect that a successful outcome may yet be achieved.  And, to judge by Mr Cameron's statement to Parliament this week, he appears to have taken this wise military counsel to heart. While the Prime Minister reiterated that he is committed to bringing British forces home at the earliest opportunity, he threw his full support behind Nato's surge strategy, warning that the British public should brace itself for further casualties during this summer's offensive.  In its first weeks in office, the Government has discovered first-hand the importance of being able to draw upon well-informed and expert military advice – assistance that was not always readily available to its predecessor. And to guarantee this advice remains of the highest calibre, it is crucial that Mr Cameron makes the right choice when he comes to appoint a successor to Air Chief Marshal Sir Jock Stirrup, the current head of Britain's Armed Forces whose early retirement was announced earlier this week.  One certainly hopes that the appointment of the new Chief of the Defence Staff is handled with considerably more dignity than the shabby manner in which Sir Jock's departure was made public.  Liam Fox, our new Defence Secretary, has made a less than convincing start to his term in office. His first visit to Afghanistan last month saw him cause enormous offence to his hosts with a reference to their "broken, 13th‑century country". The man now known throughout Whitehall as "13th Century Fox" has compounded this error of judgment by announcing the retirement of the nation's most senior serving military officer in a newspaper interview. As one of Mr Fox's critics remarked: "He does not seem to have made the transition from the freedom of opposition to the responsibility of government."  Sir Jock, who seriously miscalculated the initial military requirements for Afghanistan, is hardly the most popular member of our Armed Forces, but he deserved better than this. And Mr Fox's obvious lack of judgment has raised questions about his suitability to be involved in one of the most important appointments to be made in a generation. The next military chief will not only have responsibility for Afghanistan: he will oversee implementation of the most radical restructuring of our Armed Forces since the end of the Cold War.  On paper, the decision should be a straight choice between two high-ranking generals, not least because the bulk of Britain's military effort is at present concentrated on prosecuting a land war. Air Chief Marshal Stephen Dalton, the head of the Royal Air Force, is unlikely even to merit consideration as the notion of replacing one former fighter pilot with another could easily provoke open mutiny within the ranks. Admiral Sir Mark Stanhope, the First Sea Lord, has a better case to make, not least because, on the Buggins's turn principle, the Senior Service should occupy a position whose two previous occupants have been drawn from the RAF and Army. Indeed, Mr Fox is said to have been impressed by the arguments presented by the powerful Navy lobby. But Sir Mark is nevertheless hampered by a lack of operational experience, and by the perception that he does not possess the demonstrable leadership qualities needed for the job.  On that basis, the clear front-runner should be General Sir David Richards, the charismatic current Army chief whose operational experience as a former Nato commander in Afghanistan could prove to be invaluable. But Sir David also has a reputation for speaking his mind, a virtue that might not be appreciated by a Government anxious to avoid controversy. That would leave the way open for General Sir Nicholas Houghton, who currently works as Sir Jock's number two. Sir Nicholas is regarded as a smooth Whitehall operator – a "civil servant in uniform" is how one of his detractors put it – which explains why he is virtually unknown beyond Westminster. His main handicap is his close association with the MoD's well-documented litany of errors, in Iraq as well as in Afghanistan.  What is beyond doubt is that Britain is entering a crucial stage in this nation's proud military history, one that will demand strong, effective and professional leadership. Which is why, personally, I hope that Mr Cameron has the political courage and good sense to appoint Sir David the next head of our Armed Forces.
With the war in Afghanistan on course, it is vital that David Cameron picks    the right Chief of the Defence Staff, writes Con Coughlin.