Bearing Churchill's autograph, the memo was signed at the height of the November 1910 riots, which remain a controversial subject. It is expected to sell for £1,000-1,500 ($1,631-2,446).
The memo was written in response to a note sent by the Cardiff correspondent of the Daily News, who states that he has been informed that Churchill, then-home secretary, "has sent an order to Pembroke Dock Arsenal to get ready several thousand rounds of ball ammunition for the use of the troops drafted into South Wales".
Addressing AG Gardiner, the editor of the newspaper, Churchill responds: "My dear Gardiner,/ Give no credence to such rubbish. I do not anticipate any shooting & have taken some responsibility to that end - which Liberal newspapers should recognise/ Yours vy trly/ WS Churchill."
On November 8, 1910, local police quelled a protest by striking Welsh miners with the use of truncheons in Tonypandy Square in Cardiff. The local authorities called upon Churchill to send in the army, but he instead answered with a number of Metropolitan Police and cavalry, hoping to dissipate the anger.
However, a local magistrate requested further military back up and the riots were eventually broken up with excessive force, though there is no evidence that shots were fired. The action, which remains the subject of much debate, was seen as an unnecessarily harsh move by the liberal government, and caused ill feeling toward Churchill in Wales for the remainder of his career.
Conversation surrounding the incident persisted, to the extent that almost 40 years later, Churchill addressed the issue on his general election campaign in Cardiff, stating: "When I was home secretary in 1910, I had a great horror and fear of having to become responsible for the military firing on a crowd of rioters and strikers. Also, I was always in sympathy with the miners..."
The memo comes as part of Bonhams' Books, Maps, Manuscripts and Historical Photographs auction.
This Winston Churchill-signed letter was written during his time as secretary of war. In contrast to the Tonypandy Riots, it shows Churchill's more compassionate side, as he protests on behalf of foreign troops returning from the first world war.