Probably the largest Copperhead group was the Knights of the Golden Circle. Formed in Ohio in the 1850s, it became politicized in 1861. It reorganized as the Order of American Knights in 1863 and again in early 1864 as the Order of the Sons of Liberty, with Vallandigham as its commander. One leader, Harrison H. Dodd, advocated violent overthrow of the governments of Indiana, Illinois, Kentucky and Missouri in 1864. Democratic Party leaders and a Federal investigation, thwarted his conspiracy. In spite of this Copperhead setback, tensions remained high. The Charleston Riot took place in Illinois in March 1864. Indiana Republicans then used the sensational revelation of an antiwar Copperhead conspiracy by elements of the Sons of Liberty to discredit Democrats in the 1864 House elections. The military trial of Lambdin P. Milligan and other Sons of Liberty revealed plans to set free the Confederate prisoners held in the state. The culprits were sentenced to hang, but the Supreme Court intervened in "ex parte Milligan", saying they should have received civilian trials.