The brothers successively acquired shares in companies in the coal, paper, glass and chemical industries.
In 1894, Isidor Petschek was elected to the supervisory board of Brüxer Kohlen-Bergbau-Gesellschaft as vice president.
[1] The company's shares were among the Petscheks' most important objects of speculation on the Vienna Stock Exchange.
He left grammar school after the 6th grade, but had inherited a great entrepreneurial talent and his father's ruthlessness in business.
In 1913, Ignaz Petschek succeeded in the spectacular takeover of Hohenlohe Werke AG in Upper Silesia, thereby penetrating the East Elbe lignite region without the involvement of his brothers.
Together they founded the "Prager Kommorzgesellschaft GmbH" in 1917 to manage their financial transactions and in the same year, demonstratively in their brother's territory, the "Aussiger Montangesellschaft mbH".
In addition, Isidor and Julius Petschek acquired the majority of shares in Nordböhmische Kohlenwerke AG in Brüx and, following the complete takeover of Montan- und Industrialwerke A.G., vorm.
Starck, they gained a decisive position in the Falkenau coalfield, the second largest lignite basin in what was then Austria-Hungary.
After the First World War, Isidor and Julius acquired interests in many other industrial and financial sectors throughout Europe.
[6] His uncle Julius entrusted him with the administration of all the joint property, including the management of the Petschek & Co. bank.
[7] The Petscheks from Prague then sold their shares in the company in Central Europe and established themselves first in England and from 1938 in the USA.