O'Connor's Gunners was a short lived strike force established by the Chicago Police Department to combat organized crime in Prohibition-era Chicago. In 1927, at the height of the gang war between the Chicago Outfit and the North Side Gang, newly appointed Chief of Detectives William O'Connor convinced Mayor William "Big Bill" Thompson to authorize the creation of an elite police unit that would be able to match the firepower of the warring gangsters. Its handpicked volunteers, many former World War I veterans, would be armed with machine guns and armored cars.