By Victoria Bone
The Ministry of Defence has been criticised for failing to protect British troops from "devastating" friendly fire incidents.
L/CoH Matty Hull was killed by friendly fire near Basra, Iraq
In response, the MoD insists the problem of identification on the battlefield is a complex one which has no single, easy solution.
Defence analyst Charles Heyman points out that friendly fire deaths have plummeted since World War II.
"On D-day there were probably hundreds; in Normandy, thousands," he says.
So, in modern conflict, how do troops spot another "friendly" through the "fog of war"?
And what new technology is in the pipeline that could help save lives?
There is no single system responsible for picking out a friend or foe.
Instead several systems - for communications, weapons targeting and so on - help build up a picture for the pilot, captain or driver who then draws on his training and experience to decide whether to press the trigger.
An MoD spokesman said: "The man in his car has satnav to tell him where he is, but there isn't a satnav for the military and there couldn't be. There's just too much data.
"The way it works is that if you are on a battlefield you shouldn't be a target unless you can be positively identified as a baddie.
"If it was the other way round and you had to mark yourself out as friendly, you could become a target if there was a technical problem with your system. The military would never want that."
The simplest markers of a friendly vehicle - be it land, air or sea - are big orange panels emblazoned on the body.
"They're very visible and if you've got an orange panel everyone knows you're a friendly," the spokesman said.
However, that wasn't the case for Lance Corporal Matty Hull who died in 2003 when an American aircraft fired on his vehicle.
A cockpit video revealed the pilot had seen his orange panels, but was told by commanders on the ground that there were no friendlies in the area.
Mr Heyman, editor of Armed Forces of the United Kingdom, said no country had yet developed a fool-proof system to identify friendlies.
"Technologically, it's a terribly difficult business, because if you have any sort of electronic device which says, 'I'm here, I'm friendly, don't shoot', it's also going to be picked up by the enemy who can pinpoint your location and target you."
Since 2002, the MoD says advances have been made.
Firstly, a new radio system - BOWMAN - has been introduced, which according to the MoD, "removes any doubts regarding the location of our own forces".
It is said to allow troops to communicate more effectively with each other and with commanders to improve their "situational awareness".
Secondly, Successor Identification Friend or Foe (SIFF) equipment is being rolled out to aircraft and marine vehicles.
Described as "an electronic question and answer system", it sends a radar signal to any unidentified target to which a friendly will respond automatically with a coded reply.
SIFF equipment is being fitted to more than 1,000 ships, submarines, aircraft, helicopters and missile systems, at a cost of about £500m.
The downside is that it is not suitable for identifying ground vehicles - like the one in which L/CoH Hull died.
The MoD said: "There's just too much data from the ground - too many men, tanks, armoured cars - to process in any meaningful way. It would be impossible to get a real-time picture."
So-called "blue force trackers" are also installed in vehicles and aircraft to emit a beacon that can be detected by other friendly troops.
And individual soldiers are identifiable via infra-red tabs which can be picked out by thermal imaging and night vision cameras before an area is bombed.
American forces have introduced a system called Cooperative Engagement Capability (CEC) which allows them to make better use of their existing sensors and communication devices to avoid friendly fire incidents.
A UKCEC project is currently in the assessment phase and the MoD is considering whether it should be commissioned to put British and American troops on a technical par.
Meanwhile, in the US, Pentagon engineers have developed a second system which uses a cockpit video transmitter to allow air controllers on the ground to see exactly what the pilot sees from the air.
This Remotely Operated Video Enhanced Receiver (Rover) allows the controller to flag up both designated targets and innocent bystanders to the pilot before he fires.
Despite technological progress, the MoD says the military will always regard the human brain - and its training - as the most important factor.
So vital is the human element that something as simple as a laminated "combat identification card" is considered key to remind them of what they have learned about friendly fire.
Mr Heyman said: "It's probably wrong to go for a technological solution at all.
"Although it's impossible to eliminate friendly fire deaths, if people are properly trained, they can be greatly reduced."