The Great Illegals were a group of Soviet Comintern espionage agents whom MI5 counterintelligence agent Peter Wright grouped together due to their masterful espionage activities against the west.
[1][2][3] Often, they were generally foreigners but held Russian citizenship and were ideologically driven.
Wright considered them the best recruiters and controllers (espionage directors) that Soviet intelligence ever produced.
[1] They knew each other, and together they recruited and built a number of high-grade espionage networks in hostile foreign countries, across the world.
[1] Examples of these were, Arnold Deutsch who recruited Kim Philby of the Cambridge Five in Britain[4] the Red Three (Rote Drei) in Switzerland run by Alexander Radó or Leopold Trepper's network the Red Orchestra (Rote Kapelle) in German-occupied Europe, and Richard Sorge's espionage network in China and Japan.