In late April 1945, during the last days of the fighting in the Battle of Berlin, Haase, with Ernst-Günther Schenck, worked to save the lives of the many wounded German soldiers and civilians in an emergency casualty station located in the large cellar of the Reich Chancellery. During surgeries, Schenck was aided by Haase. Although Haase had much more surgical experience than Schenck, he was greatly weakened by tuberculosis, and often had to lie down while giving verbal instruction to Schenck.