Democratic Convention riots in Chicago, 1968.
Caption from TIME. Police wearing masks advance through tear gas clouds in Chicago's Lincoln Park.Art Shay—The LIFE Images Collection/Getty Images
Democratic Convention riots in Chicago, 1968.
Democratic Convention riots in Chicago, 1968.
Democratic Convention riots in Chicago, 1968.
Democratic Convention riots in Chicago, 1968.
Democratic Convention riots in Chicago, 1968.
Democratic Convention riots in Chicago, 1968.
Democratic Convention riots in Chicago, 1968.
Democratic Convention riots in Chicago, 1968.
Democratic Convention riots in Chicago, 1968.
Caption from TIME. Police wearing masks advance through tear gas clouds in Chicago's Lincoln Park.
Art Shay—The LIFE Images Collection/Getty Images
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See Vivid Color Photos From the 1968 Democratic Convention Protests

Heading out of the 1968 Democratic National Convention in Chicago, the message of TIME's portfolio of photographs could be reduced to one sentence: "The images of Chicago will haunt the Democrats during the campaign," the magazine declared.

Nearly a half-century later, as the Democratic Party once against meets to officially select a nominee for President, that message is still true to an extent. The 1968 Chicago convention remains a key reference point for all the ways a political convention can go wrong—in particular when it comes to protests and violence on the streets. That year's convention, which was also covered photographically in the pages of LIFE Magazine, was the scene of what TIME called "sanctioned mayhem" when left-leaning protesters clashed with the heavy-handed Chicago police force.

As TIME put it in the story that accompanied these images:

With billy clubs, tear gas and Mace, the blue-shirted, blue-helmeted cops violated the civil rights of countless innocent citizens and contravened every accepted code of professional police discipline.

No one could accuse the Chicago cops of discrimination. They savagely attacked hippies, yippies, New Leftists, revolutionaries, dissident Democrats, newsmen, photographers, passersby, clergymen and at least one cripple. Winston Churchill's journalist grandson got roughed up. Playboy's Hugh Hefner took a whack on the backside... The police even victimized a member of the British Parliament, Mrs. Anne Kerr, a vacationing Laborite who was Maced outside the Conrad Hilton and hustled off to the lockup.

..."The force used was the force that was necessary," insisted Police Superintendent James Conlisk Jr.

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Chicago's Mayor Richard J. Daley was seen as a man behind the method. By TIME's count, he had grown the 11,900-man Chicago PD with 5,000 state National Guardsmen and 6,500 federal troops. The apex of the confrontation came the night that the convention would nominate Hubert Humphrey for president, as demonstrators, deciding what to do when refused a permit to march to the convention hall, were cornered by thousands of officers.

TIME's cameras were there throughout the violent week, capturing images like the ones seen here.

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