Mitsubishi had been established in 1870, two years after the Meiji Restoration, with shipping as its core business. Its diversification was mostly into related fields. It entered into coal-mining to gain the coal needed for ships, bought a shipbuilding yard from the government to repair the ships it used, founded an iron mill to supply iron to the shipbuilding yard, started a marine insurance business to cater for its shipping business, and so forth. Later, the mangerial resources and technological capabilities acquired through the operation of shipbuilding were utilized to expand the business further into the manufacture of aircraft and equipment. Similarly, the experience of overseas shipping led the firm to enter into a trading business.
The company bought into coal mining in 1881 by acquiring the Takashima mine and Hashima Island in 1890, using the production to fuel their extensive steamship fleet. They also diversified into shipbuilding, banking, insurance, warehousing, and trade. Later diversification carried the organization into such sectors as paper, steel, glass, electrical equipment, aircraft, oil, and real estate. As Mitsubishi built a broadly based conglomerate, it played a central role in the modernization of Japanese industry.
The merchant fleet entered into a period of diversification that would eventually result in the creation of three entities:
- Mitsubishi Bank (now a part of the Mitsubishi UFJ Financial Group) was founded in 1919. After its mergers with the Bank of Tokyo in 1996, and UFJ Holdings in 2004, this became Japan's largest bank.
- Mitsubishi Corporation, founded in 1950, Japan's largest general trading company
- Mitsubishi Heavy Industries, which includes these industrial companies.
- Mitsubishi Motors, the 6th largest Japanese auto manufacturer.
- Mitsubishi Atomic Industry, a nuclear power company.
- Mitsubishi Chemical, the largest Japanese chemicals company
- Mitsubishi Powersystems, a power generation division
