[2] In 1932 he was an instigator of the so-called Urgent Call for Unity ("Dringender Appell für die Einheit"), a public appeal, signed by 32 high-profile intellectuals, urging the principal left wing parties to unite ahead of the first 1932 General election in order to block Nazi success.

[4] Gustav Heckmann was born into a traditional "church and emperor" family at Voerde, a town in the industrial Rhineland region, at the extreme western edge of Germany.

[1] Two years later, after complying with Nelson's non-negotiable condition that he cut all ties with the church, which had led to protracted wrangling with his parents,[3] Heckmann was accepted as a teacher at the "Walkemühle" Philosophical-Political Academy in 1927.

[6] Heckmann's life experiences would lead him to develop Nelson's methodology of political philosophy towards his understanding of its Socratic basis, and a more practical and less absolutist search for truth.

[3] The outcome of the 1930 General election came as a huge shock for Heckmann[3] whose activities, along with those of his ISK colleagues, quickly acquired a more political focus, while his teaching work at the "Walkemühle" was suspended.

[3] In 1932, backed by Minna Specht and Hellmutt von Rauschenplat who also taught at the academy, Heckmann instigated the publication in a newspaper of the ISK's Urgent Call for Unity ("Dringender Appell für die Einheit"), a public appeal, signed by 32 high-profile intellectuals, urging the Social Democratic and Communist parties to unite ahead of the first 1932 General election in order to block Nazi success.

[3] Much of the text was drafted by Heckmann himself, including a prescient and resonant warning referencing Schiller against allowing inbuilt inertia and cowardice of the heart to leave the way open for a decline into barbarism.

[1] While Eichler fled to Paris, Minna Specht and Gustav Heckmann escaped together to Denmark, accompanied by the children's section of the academy.

The number of refugee schoolchildren accompanying them to Denmark was initially 15, but this increased little by little over the next couple of years to approximately 25,[3] of whom roughly 50% were Jewish: along with teaching and maintaining the old manor house, Specht and Heckmann devoted themselves to seeking out Danish families who might be able and willing to look after Jewish children and other children of exiled or disappeared German left-wing activists, in the event of a German invasion.

[3] His duties with the Pioneer corps included transporting concrete blocks, and other building work in connections with the construction of nissen huts.

He was a speaker at the 1960 demonstration at the Bergen-Hohne Training Area, remembered as an early "star march" ("Sternmarsch") for which protesters converged from various different starting points including, in this case, Hamburg, Bremen, Braunschweig and Hannover.