He worked as a technical engineer in a Swiss aluminium factory, and then as a manager in a small electro-chemical firm in Bitterfeld, where he conducted experiments in electrolysis. He returned to Berlin and joined the AEG board in 1899, becoming a leading industrialist in the late German Empire and early Weimar Republic periods. In 1903 his younger and much more entrepreneurial brother Erich Rathenau died. Heart-broken, his father had to be satisfied with Walther's help instead. Walther Rathenau was a successful industrialist: in only a decade he set up power stations in Manchester, Buenos Aires, and Baku. AEG acquired ownership of a streetcar company in Madrid; and in East Africa he purchased a British firm. In total he was involved with 84 companies worldwide. AEG was particularly praised for vertical integration methods and a strong emphasis on supply chain management. Rathenau developed an expertise in business restructuring, turning companies around. High organizational capabilities made his company very rich, and it produced the standards for new chemicals development, such as acetone in Manchester. He made large profits from commercial lending on a wide industrial scale, and those profits were reinvested in capital and assets.