Rieboldt informed Michaelis about armaments work at Blohm + Voss, particularly regarding the construction of airplane motors and warships.

The goal of the Resistance group around Michaelis was to expose to the world the Nazi's secret involvement in the Spanish Civil War.

[1] Biermann and his brother-in-law, Karl Dietrich, a ship captain, reported to Michaelis on the weapons shipments from January to March 1937 to Francisco Franco.

Michaelis relayed this information in January and February 1937 through a middle man, Richard Bähre, who, in turn, forwarded it to the exiled KPD leadership in Basel.

Michaelis is included in the names on the monument unveiled in 2007, honoring the lawyers who perished at the hands of the Nazis.