TONY Blair once compared the effect on world affairs of September 11, 2001, to the shaking of a kaleidoscope.
A better comparison, it seems now, would have been the upending of a snow globe. The storm that began that late summer day is still raging. From Britain to America, from Helmand in Afghanistan to Fort Hood in Texas, scene of the latest soldier-on-soldier deaths to hit the US Army, the pieces continue to fall, some landing more softly than others.
There was a familiar, grim choreography at work as reports of what had happened at the base began to come through. As with the previous attack at Fort Hood in 2009, in which 13 soldiers were killed and 32 wounded by Nidal Hasan, the news broke in the wee small hours, UK time.
There were scenes of anxious families rushing to the camp and officials scrambling to deliver statements. The who, how, where, what and why of journalism began as the dead and injured were counted. Having killed three and injured 16, the gunman turned his weapon on himself.
President Obama told the country the authorities were trying to get to the bottom of exactly what had occurred, saying: "We are heartbroken something like this could happen again."
In certain respects, the 2009 killings and this week's events are different. Hasan's actions were those of a terrorist. According to him, he wanted to kill his former comrades before they could kill the Taliban. In the case of the latest Fort Hood deaths, details of the gunman are still emerging.
What is known is that he served for four months in Iraq and was being treated for mental health problems while doctors tried to determine whether he was suffering from post-traumatic stress disorder. If that turns out to be the case, and his mental trauma is linked to his time in Iraq, then it might be said he was another casualty of war.
Other casualties of war are not so clear cut or as easily quantifiable as a lone gunman. This week, British forces handed military command in Helmand province to the Americans. The ceremony was brisk, the changing of the guard sealed with a handshake. This was history being marked in a hushed, downbeat way, as if the last thing anyone wanted was to draw too much attention to the event.
Yet this was a conflict in which 448 British personnel, men and women, lost their lives, the last death occurring on March 5 this year. That is 448 families shattered, never to be mended. Wives widowed, sons and daughters lost, children who will never see their parents again, brothers and sisters bereft. Pain and loss stretching beyond what the mind can imagine. How does a society even begin to measure, never mind mark, such a loss? Then comes the long line of the injured, some with life-altering wounds, mental and physical.
It is telling that the sotto voce handover of Helmand should occur as the UK prepares to mark the centenary of the First World War with as much pomp and ceremony as the occasion demands. Some £50 million is being spent with events ranging from exhibitions to a service attended by Commonwealth heads of state in Glasgow Cathedral. Many do not begrudge a penny of that money, seeing it as a demonstration of the respect that is due. One does wonder, however, how the end of the conflicts in Iraq and Afghanistan will be marked when their centenary dawns. Who will remember the fallen from those wars? How will those sacrifices be explained?
Afghanistan, Iraq, the so-called war on terror of which these two conflicts were a part: the snowflakes continue to land where they may. In the US, after four years of investigation, the report of the Senate intelligence committee into CIA interrogation techniques and strategy continues to inch its way towards publication. According to a Washington Post story this week, the committee asks whether the methods worked in saving lives and pre-empting plots, and comes back with the answer "no". All those moral red lines crossed, all that damage to the reputation of the West, a toxic legacy that will last for generations, and for what end?
Unlike the First and Second World Wars, the "war on terror" declared by George W Bush and Mr Blair has no clear end. Its beginning was all too painfully apparent, but its denouement remains out of sight. It has not left office with a big pension. It is not off building a library in its own honour, or making speeches around the world for international telephone number fees. Just as one starts to think that the ripples from Afghanistan and Iraq are disappearing, along comes a reminder we are a long way from that point. Sometimes, those reminders emerge in the unlikeliest of settings, such as the Farage-Clegg televised bunfight, the second part of which took place this week. As debaters, this pair made Johann Lamont and Nicola Sturgeon look like Plato and Socrates. But amid the bluster and bellyaching there was one significant point made.
Although the debate was meant to be focused on the forthcoming European elections, the ranting ranged all over the map, with Nigel Farage, the Ukip leader, lambasting Nick Clegg, Deputy Prime Minister, for being part of a political establishment only too keen, in his view, to drag the country to war. Fixing the deputy prime with a glare, Mr Farage said: "This country, Nick, has had enough of getting involved in dangerous foreign wars. There is no evidence that our military intervention in these countries is making things better. With you as deputy prime minister we bombed Libya, and it is worse now than it was then." While Mr Clegg looked flushed and exasperated, one could not but feel that out there in Voterland, the Ukip leader had scored a direct hit. Post-Afghanistan, post-Iraq, the UK, in common with other western countries, has developed an allergy to conflict, be it in Libya, Syria, or elsewhere. This has happened to such an extent that the likes of Mr Farage, who could otherwise be expected to wrap himself in the flag at the first opportunity, comes across as a peacenik while a Liberal Democrat deputy prime minister looks like the aggressor. The globe is shaken, the politics are topsy-turvy, the snowflakes settle.
The impact of Afghanistan and Iraq on British politics remains incalculable. It can be seen in the country's attitude to intervening abroad. It is there in the way voters regard the political establishment that sent British forces to those countries to no clear purpose or end. It can even be counted in monetary terms in the debt accrued, all those billions spent.
There is no doubt, however, who has paid the greatest price, be they serving soldiers or civilians. The families of the dead, and the injured, carry on with life as best they can. That kind of suffering does not come to an end easily, and it certainly does not stop with a handshake and a military handover.