By Peter Caddick-Adams
It was the first case of "friendly fire" by British air support in Afghanistan
Last week a British Army helicopter accidentally fired on UK paratroops in southern Afghanistan, wounding nine. But such "blue on blue" incidents are not new - they have long been an unfortunate consequence of the fog of war.
The recent friendly fire episode in Helmand underlines one of the basic facets of all military operations. In the confusion, chaos and uncertainty of war, sometimes your colleagues get in the way and you end up hurting them instead of the enemy.
In today's litigious world it's right to ask questions and convene boards of enquiry to minimise such disasters, but it won't stop them.
The military call them "blue-on-blue", after the colour used to denote friendly forces on maps (the enemy are always marked in red).
The Prussian military thinker Carl von Clausewitz 200 years ago established that war is chaotic in nature and therefore all the norms of peacetime training are overwhelmed in the sometimes literal fog of battle.
Soldiers often can't see what is going on around them; communication even in modern battle is frequently difficult, if not impossible, and instant decisions must be made. Given more clarity and time, those split-second decisions might be made differently, but with a threat materialising and the lives of colleagues at risk, you have to do something - and fast.
Bader shot down
Chroniclers of the battle of Waterloo, fought in 1815, have recorded how British infantry squares engaged one another by mistake and other allied cavalry, causing many casualties.
Douglas Bader, thought to have been shot down by fellow airmen
Similar incidents happened in the Crimea in 1854, during the American Civil War of the 1860s and the Boer War of 1899-1902. War diaries from World War I are peppered with accounts, mainly of British artillery shelling British troops by accident, poison gas clouds being misdirected, or a worn gun barrel firing shells inaccurately.
In World War Two, many allied aircraft were lost to so-called friendly fire, because of poor aircraft recognition skills, or the split seconds in which a pilot had to decide whether to engage an oncoming plane or not.
Historians now think that the famous RAF fighter ace Douglas Bader was shot down by one of his wingmen, not the Germans. Similarly, allied aircraft engaged and sank a whole squadron of allied minesweepers off the French coast in 1944, through recognition problems. All sides lost even submarines to their own forces.
Deaths caused in this way are particularly distressing as they are clearly avoidable, so some kind of formal enquiry is always held - even in a world war. The aim is less to establish blame, but tighten up on procedures to ensure the mistake is not repeated.
Of course, each time the Germans introduced a new aircraft design that resembled the silhouette of an allied plane, the risks started all over again. When the United States military sensibly introduced camouflage suits in Normandy in 1944, they suffered many casualties because until then the only troops to wear camouflage in combat were the Nazi SS. The new uniforms were hastily abandoned.
The US's most senior officer to die in WWII was a lieutenant-general, bombed - with several hundred others - in error by his own air force in July 1944, prior to a big ground offensive.
Secrets and apologies
Military historians estimate that casualties caused by friends, not enemies, may amount to between 2-3% of battle deaths in the two world wars.
John Simpson flees an attack from a US warplane in Iraq in 2003
The issues associated with friendly fire casualties are the constant need to educate troops on the battlefield about new equipment - and new coalition partners - which may be mistaken for an opponent, and the speed with which one has to react. This often makes it difficult to assign blame to any individual. These factors make it difficult to conceive of wars fought without such casualties.
On the other hand, where we can do better in matters of friendly fire is in how the incident is handled once it has happened. The inclination is for armies and governments to close ranks and obscure the event with the need for operational security. The US government, for example, has been notoriously reluctant in recent years to release camera footage of their aircraft engaging ground targets that turned out to be friendly.
And when the next-of-kin of a helicopter crew shot down in the 1982 Falklands War eventually found that the culprits were British, not Argentinean, they found the truth so much more painful to bear. The hurt was more exaggerated because they had to fight the Ministry of Defence to establish the cause of death of their loved ones.
The MoD is investigating how the Helmand paratroopers came under fire
Technology can help, with devices now in service that establish the identity of every friendly soldier and vehicle on the battlefield. However, their tracking batteries can still fail at a crucial moment, and the signals they emit can be obscured by poor weather, mountains and buildings.
Additionally, each coalition partner procures such technology separately, with the result that not all these systems interface.
It is difficult to find words to console those wounded by friendly fire in Helmand, or their relatives, and impossible to state that it won't happen again, but we do now seem to be more forthright in reporting such incidents.
Perhaps the best to hope for, in that unique, terrible world of combat, is a swift, heart-felt apology to all concerned from those at the very top, whichever nation they belong to.