In a ruthless and devastating bombing campaign against Kurdish rebels in northern Iraq and Indian tribesman on the North-west Frontier, the RAF killed thousands of civilians and razed many villages.
It is clear that air force despatches describing the extent of casualties were deliberately censored to avoid criticism by Parliament, which was worried by rumours of indiscriminate bombing.
A Channel 4 television documentary 'Birds of Death', part of the Secret History series, which is broadcast tonight, cites previously unpublished secret documents to prove that Sir Hugh Trenchard, Chief of the Air Staff at the time, and the Air Council doctored operational reports before they were submitted to the Air Minister and Parliament.
Wing Cdr Gale, of 30 Squadron, Iraq, told George Case, the film-maker: 'If the Kurds had not learnt by our example to behave themselves in a civilised way, then we had to spank their bottoms. This was done by bombs and guns.'
The Kurds, who had no defence against the biplanes, were fighting for independence, shortly after their forced inclusion in the new state of Iraq, which was under British mandate.
In 1924, Arthur 'Bomber' Harris, later head of Bomber Command during the Second World War, was flying as a wing commander against the Kurds. He wrote: 'The Arab and the Kurd now know what real bombing means in casualties and damage. Within 45 minutes a full-sized village can be practically wiped out and a third of the inhabitants killed or injured by four or five machines.'
But the British Government was deprived of full knowledge of the extent of those casualties. Winston Churchill, the Air Minister, was perturbed by reports of atrocities. He wrote to Sir Hugh Trenchard, who responded by censoring reports.