I had very little understanding of events in Northern Ireland while studying for my A-levels at a state grammar school in Guildford in 1972. My subsequent time at Sandhurst left me none the wiser. Entering military academy later that year, I assumed that I was embarking on a well-worn trail in the relationship between ethics and military duty. Of this I was quickly disabused.

A young ‘tom' was a witness, a prosecutor, jury, judge, and if required, executioner, all in a matter of a split second

As officer cadets we trained in internal security drills, which usually ended with direction to shoot dead the “demo” Gurkha soldier, ringleader of a rioting mob – conveniently wearing a red T-shirt. This was taught doctrine at that time and was repeated in later training. Small wonder, perhaps, that some soldiers may have been under the impression that killing rioters was accepted army doctrine.

My first tour of Northern Ireland as a second lieutenant with 2 Para (2nd Battalion, Parachute Regiment) in June 1973 was quite an eye-opener. As a young officer I swallowed whole the regimental line that soldiers from our first battalion had been under attack during a civil rights march in Derry in 1972, on what became known as Bloody Sunday, and responded accordingly with lethal force. I had no knowledge at all of a previous incident in Ballymurphy in August 1971 – later referred to as a massacre – in which 10 civilians were shot dead allegedly by paratroopers in the small west Belfast neighbourhood during disturbances prompted by the introduction of internment without trial.

In more recent times these events have been the focus of greater media and judicial interest. I have read both the Widgery and the Saville reports into Bloody Sunday, and for reasons not well explained the responsibility of the army chain of command seems wholly absent.

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In fairness to the army, most officers and soldiers, for most of the time, have performed commendably in very difficult circumstance between 1969 and 2007 – the formal end of British forces’ operations in Northern Ireland. Some have not. And in the event that a command ethos of brutality and murder takes over, we should not be all that surprised at the consequences. This to me is the essence of Bloody Sunday, where specific orders were ignored, an officer opened fire above Rossville Flats – contrary to law – and then the “Derry effect” of those gunshot echoes probably convinced other soldiers that they were indeed under fire. I am not blaming the then commanding officer, alone, for this insubordination .

As a young officer, having got quite a lot of Northern Ireland experience under my belt, I decided, in the absence of any guidance, on my own “doctrine”: I talked to my various platoons, my company and then, from 1994-1997, my battalion, about ethics and military duty. At each level I attempted to make clear that the authority and power in the use of lethal force, at just 18 years old, was awesome. In situations where life was endangered or lost, a young “tom” was in effect a witness, a prosecutor, jury, judge and, if required, executioner, all in a matter of a split second.

In recent times quite a few veterans, especially from the Parachute Regiment, have argued that their actions under duress should not be subject to legal scrutiny. The usual line is about their age, memory, time, witness reliability – if still alive – and that these issues are best left in the past. I do not share that view – and the government has rejected previous claims of amnesty.

Charles Townshend, a leading historian on British counterinsurgency, writes in Britain’s Civil Wars (1986) that the country has never accepted anything other than that complete legal responsibility at all times underpins the morale and discipline of our armed forces. Take this away in the context of operations in Iraq and Afghanistan, and it would be akin to the US forces in Vietnam. That we should not go down such a hazardous road is, to me, all too obvious. This year we are commemorating the centenary of Amritsar, where so clearly Colonel Reginald Dyer did in every respect abandon our common-law heritage. We can never, ever, risk such a repetition.

The recent government white paper on these issues seems to me to cloud all this – offering the notion that legal accountability can be applied in Northern Ireland but nowhere else. The connection between Bloody Sunday, the Falklands war and Afghanistan is the extent to which senior officers did their best to cover up incidents of serious crime when committed by soldiers – a manifest failure of legal and ethical standards expected of serving officers of all ranks. “Put up, shut up, cover up,” is the unofficial doctrine.

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The defence secretary, Penny Mordaunt, is attempting to strengthen legal protections for troops facing investigation over alleged historical offences – but veterans of Northern Ireland won’t be covered by this. General Lord Dannatt claims he is serving the interests of the army by challenging the plan in the House of Lords: he argues that Northern Ireland should also be exempt from the law because all theatres of war need to be treated the same. Surely the argument of a former chief of the general staff should be that all cases of serious crime committed by our soldiers be investigated and, if need be, prosecuted – without exception. Only on this basis can high morale and good discipline be ensured.

A comparison with supposed amnesties regarding terrorists is simply missing an obvious point: the armed forces are intended to represent the law in situations where law has been absent through usual means. The problem here is that a prevalent ethos of “regimental loyalty” can supersede all other considerations, and that exposing wrongdoing is thus disloyal – historical accounts of the British army during the Troubles have made this clear. This can only be countered by investing in an ethical education for all ranks of the armed forces. Defence humanists can only agree with this cause.

• Colonel David Benest was commanding officer of 2nd Battalion, Parachute Regiment, from 1994 to 1997