No weapon of pistol calibre can ever replace the rifle as the infantryman's main arm. Its issue will be limited to those who, for some reason or other, cannot carry a rifle. No 'Pistol gun' [submachine gun] resembling this particular weapon is required in the British Army, since it is apparently designed as a substitute for rifles or auto rifles.
From a 1919 report from the British Army’s School of Musketry at Hythe, on the German MP18.I submachine gun. The British army failed to understand the practical application of the submachine gun as a supplement to the infantry sections firepower.
Instead, the British Army saw the submachine gun as a carbine, to be issued to troops that didn’t need or couldn’t carry a rifle. They failed to appreciate the submachine gun’s potential. The British would later describe submachine guns as ‘machine carbines’ - a practice that continued into the early 1950s.
A Thompson M1921 being demonstrated to British officers and men at Bisley in July 1921 (source)
As a result the British Army maintained an ambivalent and dismissive attitude towards submachine guns throughout the interwar period and entered the Second World War without a submachine gun.
Source:
The Schmeisser Myth, M. Helebrant, (2016)
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