4:56pm UK, Friday August 14, 2009
The British death toll in Afghanistan stands at 199 since the conflict began
The unnamed officer wrote the emotive article in Monday's Independent newspaper.
"My motivation is simple" he said.
"Writing this helps vent off some of the frustration at what is happening out here in Afghanistan to those serving in the British Army, where death and serious injury are sickeningly common occurrences."
The officer, who has been in the Army for eight years, is likely to be brought back from Afghanistan and faces disciplinary action and a possible court martial.
It is thought he was identified because he revealed the unit he was serving with - the 1st Battalion Welsh Guards Battle Group.
He wrote in detail about coping with the loss of fellow soldiers and the injuries sustained by many more.
"I am talking about limbs removed, double or even triple amputations, on a scale that we've never seen before," he said.
Serving members of the Armed forces are banned from speaking to the media without prior agreement from the Ministry of Defence.
Roll Of Honour 2009
All the servicemen and women who lost their lives in Afghanistan in 2009.
But just this month, new guidelines were drawn up by the Government which encouraged soldiers to talk about their work online.
An MoD press release read: "Service and MoD personnel are being encouraged to talk about themselves and their work online within new guidelines which give advice on how they can protect their security, reputation and privacy."
But the guidelines also clearly state that any communication with the media "must be referred, through the line manager/chain of command".
The captain clearly breached a number of these guidelines.
He gained no authorisation before writing the article, he questioned the purpose of the mission in Afghanistan, and he complained of a lack of equipment.
In his article he also said: "Then there are the equipment shortages. Due to the pitiful numbers of support helicopters and Apaches needed to escort them, every day troops on the ground are forced to expend an enormous amount of hours and manpower just standing still."
He concluded the article with: "We seem to know and say that it is not worth it, whilst instinctively reacting and saying that it is worth it - it has to be worth it.
"If I am honest, I do not know what I think about it all conclusively; my reasoning is lost in the storm of media, opinions, analysis that are at play here."
It is understood that he already had plans to leave the Army soon.