According to a 2011 book by Canadian historian David Leeson, "The Black Tans: British Police and Auxiliaries in the Irish War of Independence, 1920-1921," published by Oxford University Press, we have been misled by the Irish history books for almost a century.
Winston Churchill, British Secretary of State for War, sent the Black and Tans into Ireland on March 25, 1920. It was a fatal mistake by the British that drove Irish opposition to British rule to new heights.