Another significant Soviet involvement was the activity of the People 's Commissariat for Internal Affairs ( NKVD ) inside the Republican rearguard . Communist figures including Vittorio Vidali ( " Comandante Contreras " ) , Iosif Grigulevich , Mikhail Koltsov and , most prominently , Aleksandr Mikhailovich Orlov led operations that included the murders of Catalan anti-Stalinist Communist politician Andrés Nin , the socialist journalist Mark Rein , and the independent left-wing activist José Robles . Another NKVD-led operation was the shooting down ( in December 1936 ) of the French aircraft in which the delegate of the International Committee of the Red Cross ( ICRC ) , Georges Henny , carried extensive documentation on the Paracuellos massacres to France
Paracuellos massacres
Paracuellos massacres
Spanish Civil War