It must rank as one of the most insensitive Ministry of Defence decisions of all time: first announce the disbanding of one of the oldest regiments in the British Army and then order it to one of the most dangerous sectors of the war in Iraq in support of the American assault on Fallujah. That is what happened to the Black Watch in 2004.

Within days they had lost three men and a local interpreter in a suicide bombing. In the clubs and pubs of Fife and Tayside, where the young men of the Black Watch have been recruited since before Culloden, they are still angry. One of the things this magnificent, epic piece of theatre, written by Gregory Burke and directed by John Tiffany for the National Theatre of Scotland, dramatises most effectively is the old truism that soldiers do not fight for their country or for a cause but for their unit and for each other.

Burke grew up in West Fife close to the naval base of Rosyth. Many of his friends are servicemen. When he interviewed former Black Watch soldiers for this piece he will have been told things that ordinary TV researchers — one is used as a dramatic device for getting the soldiers here to tell their stories — would never have been told. The MoD will not be thrilled by the tale of the depleted uranium tank shell. Nor do the recruiting posters really describe the peacekeeping mission in Kosovo as “Club 18-30 with a gun”.

Burke has done an unobtrusively skilful job of structuring his material into two intense and emotional hours. The palpable sense of authenticity in the way the soldiers speak and the things they say is followed through in Tiffany’s explosive, inventive production. The ten performers, each as watchable as the next and yet each carefully differentiated, hurl themselves around the vast echoing drill hall, as well drilled and committed as any soldier.

There are moments too of almost balletic lyricism, such as the reading of letters home accompanied by Davey Anderson’s hugely effective music, and a brilliantly inventive section in which one soldier tells the history of the regiment while his fellows dress and redress him in the changing uniforms.

Not everyone will agree; not everyone will sympathise. But few will come away untouched by this thrilling, raw, challenging and masterful piece of work. It takes a lot to get an Edinburgh audience to its feet but they were standing to applaud this.

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