From 1921 to 1929, Reiss served in Western Europe, particularly Berlin and Vienna. In Berlin, their house guests included Karl Radek and , ex- wife of Fedor Raskolnikov (a Naval officer who chronicled the Kronstadt rebellion). In Vienna, friends included Yuriy Kotsiubynsky, Alexander Schlichter, Angelica Balabanov, Paul Ruegg, Ivan Zaporozhets, Alexander Lykov, and Emil Maurer. In Amsterdam, Reiss and his wife knew Henriette Roland-Holst, Hildo Krop, Princess Juliana of the Netherlands, "Professor Carvalho", "H. C. Pieck" (Henri Pieck), and most importantly "Henricus" or "Henryk Sneevliet" (Henk Sneevliet). In this same period, Richard Sorge brought Hede Massing to Reiss for training.