What action did the Chicago police take against hundreds of union leaders?

The action taken by the Chicago police against hundreds of union leaders was to arrest them. This response demonstrates the tensions between law enforcement and organized labor, particularly during periods of labor unrest in the late 19th and early 20th centuries. The police often moved to suppress union activities through arrests, reflecting the government's stance against labor movements at that time. This form of enforcement was used to intimidate union leaders and dismantle organized efforts to improve workers' rights and conditions, illustrating the challenges that unions faced in advocating for their members against powerful interests.