In 1935 he made Minotauromachy, an etching with engraving, where he takes up again the figure of the Minotaur seen for example in Minotaur Kneeling over Sleeping Girl from the Vollard Suite. It is considered one of the stylistic precedents of Guernica. Between 1936 and 1937 he illustrated Historia natural by Buffon (published in 1942), again commissioned by Vollard, a set of thirty-one sugar-lift etchings in a realistic style. In 1937, he made The Dream and Lie of Franco (Sueño y mentira de Franco), a set of eighteen small vignette-like images etched on two copper plates (with aquatint), as a denunciation against the Spanish Civil War and Francisco Franco; a thousand copies were printed and sold at the Spanish Pavilion of the Exposition Internationale des Arts et Techniques dans la Vie Moderne of that year.
