 When the stalemate in the trenches began, he returned home.He contacted Colonel Max Bauer, the staff officer responsible for munitions, with the idea of driving the defenders out of their trenches with shells releasing tear gas.When his idea was tried one of the observers was Fritz Haber, who argued that too many shells would be needed, it would be better to release a cloud of heavier-than-air poisonous gas; the first chlorine cloud attack on 22 April 1915 was not supported by a strong infantry thrust, so the chance that gas would break the stalemate was irrevocably gone.