i think i want to agree with
DownwardDog but my pride won't
quite let me - we failed, imv, because of five things.
numbers. UK expeditionary land capability was/is around a Brigade+support, 10,000 men. that was our peg, and we 'decided' it would fit whatever hole we came across. its worth noting that when the US got seriously involved in Helmand in 2010 they brought a force of 30,000 to augment our 10,000.
aim. not only did we not have - in the post 2002/3 situation - a clear political/military end state we wanted to achieve, but we kept changing it, and we thought that the person we'd offended with our previous plan would wipe the slate clean when it came to the next plan. they didn't.
career meets war - and war loses. Officers hoping to be promoted (and here i'm talking about Lt Col and above) not only needed to be able to demonstrate that they'd had a 'good war', but they had to demonstrate they the'd had an impact, that they'd tried something new. when these people change every 6 months, and then add their changes to the political confusion over the overall aim, the situation became constant flux. nothing stayed in place long enough to achieve anything, and even if something had shown it was working, it would be changed by the next influx of senior officers looking to put something shiny on their CV. this was known about, and constantly highlighted by the officers involved, but the promotion system at that level was never changed to understand the difference between innovation in a peacetime Army and just fucking about with stuff for the sake of it in a wartime one.
moral failure. not one of the very many very senior officers who knew it was going wrong, and that it would continue to go wrong while all the above stayed in place, resigned and went public.
political failure. our politicians decided in 2009/2010 that the war was going to end in 2014, and as long as it ended they didn't much care who won it. so the smart Taliban went home, waited till we fucked off, and will emerge to fight, and probably defeat the central government - at least in the south and east.
in terms of our people, we are the only nation involved in Helmand on any scale who did not have a position overrun by the Taliban. our people on the ground were brilliant.