 Riezler was an eyewitness to Mirbach's assassination by the Left Socialist-Revolutionaries on 9 July 1918, having unwittingly ushered the gunman Yakov Blumkin into Mirbach's presence.During this period, Riezler served as the conduit for German subsidies to the Bolsheviks and personally negotiated these with Lenin's representatives Karl Radek and Alexander Parvus.Riezler later claimed privately that it had been his own idea to transport Lenin in the famous "sealed train" from Zurich through Germany to Russia in April 1917.