From March to July 1914, he studied art restoration and it was also at this time that he began to develop his idea of “deconstruction.” This period would be interrupted however, as in early August, due to the developments of war, he was forced to return to Germany. He spent the war in the health service, but still published numerous articles, and made friends with Raoul Hausmann, Hannah Höch and those in the Dadaist circles of Berlin. True to form, he often changed address, never staying in one place too long. He continued to paint, draw and created his first engravings at this time, as well as becoming interested in the art of stained glass and monumental art.
In 1916 he married the pianist Dore Leeser with whom he had a son, Berthold. In 1918, the couple would divorce, and their son would unfortunately fall ill and die in February, 1922. After the war, he carried on with his art school, with some success, and in 1919 he organized the first Dada exhibition in Cologne with Max Ernst and Johannes Baargeld, and contributes both writings are artwork to Dadaist and expressionist magazines.