 After a truce with the British in July 1921, the IRA imported more Thompsons and used them in the subsequent Irish Civil War (1922–23).They were not found to be very effective in Ireland; the Thompson caused serious casualties in only 32-percent of the actions in which it was used.The Thompson achieved most of its early notoriety in the hands of Prohibition and Great Depression-era gangsters, the lawmen who pursued them, and in Hollywood films about their exploits, most notably in the St Valentine's Day Massacre.