By the time this rebuttal appeared Müller had resigned from the boards of "Tagafia" and of the air field company, which were the two entities drawing the most voluminous of the media criticism. He successfully pursued a number of further defamation cases against journalists, but the legal processes involved were often cumbersome and slow. War broke out in July 1914. Control of the airfield was assumed by The Army. The army commander, Captain Alfred Hildebrandt, proved to be no friend to , nor to Müller. Sources are silent about Müller's attitude to the war, but it is known that production at his LVG aircraft factory on the airfield climbed steeply. It would be hard to believe that Müller's business interests did not profit significantly from his involvement in supplying the military. In October 1918 a new company, "Luftverkehrs-Gesellschaft Kommandit-Gesellschaft Arthur Müller" was registered, presumably in anticipation of a post-war aerospace boom. The next month it became apparent the Germany had lost the war, and the "negotiations" that produced the Treaty of Versailles in June 1919 put an abrupt end to thoughts of an aerospace boom. Germany was permitted to retain 149 civilian aircraft, and the conditions imposed by the victorious powers included a complete ban on aircraft production. There were some aircraft entrepreneurs and workers who quietly switched their attention to gliders while others wondered if a more promising industrial future for Germany might lie in automobile production. With the emperor gone and the aerospace sector hobbled, it was time for new beginnings. At the end of the war Müller invested heavily in new sectors, as halls intended for balloon storage were hastily redeployed. The focus of "Arthur Müller Bauten- und Industriewerke" (AMBI), his new venture, was initially on pioneering building materials, based on innovative combinations of basic and readily available ingredients such as cement, sand, plaster, clay and coke ash. There were AMBI-bricks, AMBI-slabs, AMBI-roof tiles and AMBI-facings. Patents for the new materials were obtained, along with the necessary approvals from the building inspectorates. Müller also entered the homes construction business himself, concentrating on modern well-insulated multi-storey residential blocks. A noteworthy development on the northern edge of the airfield site included multi-occupancy blocks and detached houses, all constructed according to the AMBI-method.