 De Kadt developed into a trenchant and increasingly uncompromising critic of Stalinism, and articulated an independent line of socialist thought and political practice.This was expressed both in the content of his first major book, "From Tsarism to Stalinism" published in 1935 in Antwerp,and in his pivotal role in the formation of the Independent Socialist Party (Netherlands) (OSP).The book, which identified a continuity between the character of the Tsarist state and the Soviet political system under Stalin, contained an intimation of De Kadt's broader critique of twentieth century totalitarianism – a critique which was to define the nature of his subsequent political career.