Dissatisfied with the large concessions granted to Germany by the Bolsheviks in the Treaty of Brest-Litovsk, two Chekists who were left SRs assassinated the German ambassador to Russia, Count Wilhelm Mirbach early in the afternoon on 6 July. Following the assassination, the left SRs attempted a "Third Russian Revolution" against the Bolsheviks on 6–7 July, but it failed and led to the arrest, imprisonment, exile and execution of party leaders and members. In response, some SRs turned again to violence. A former SR, Fanny Kaplan, tried to assassinate Lenin on 30 August. Many SRs fought for the Whites or Greens in the Russian Civil War alongside some Mensheviks and other banned socialist elements. The Tambov Rebellion against the Bolsheviks was led by an SR, Aleksandr Antonov. In Ufa the SRs' Provisional All-Russian Government was formed. However, after Admiral Kolchak was installed by the Whites as "Supreme Leader" in November 1918, he expelled all Socialists from the ranks. As a result, some SRs placed their organisation behind White lines at the service of the Red Guards and the Cheka.