The Rotterdamsche Droogdok Maatschappij NV (RDM) was a major shipbuilding and repair company in Rotterdam in the Netherlands, existing from 1902 to 1996.

The Rotterdamsche Droogdok Maatschappij was a successor of the shipbuilding company De Maas, founded in Delfshaven in 1856 by Duncan Christie.

On 14 April 1899 a consortium was founded by people connected to the harbor of Rotterdam and the company De Maas.

The supervisory board accepted the offer of the consortium of 207 shares in De Maas and the terrain on Heijplaat for 101,400 guilders.

[5] For the CEO position the supervisory board wanted to have W. de Gelder working as an engineer in Kinderdijk.

He had written a brochure that advocated the need for a modern drydock company west of the railway bridges over the Meuse.

[6] The machine factory, model room and carpentry shop were located in another building on the south side of the terrain.

The steam engines and boilers were built by RDM, but the power plant as a whole was made by machine factory 'Voorheen Gebr.

[7] The assets which came in from De Maas consisted of a big inventory and many tools, and above all 300 experienced employees.

[7] On 18 July 1902 the order for two floating drydocks was given to William Hamilton and Company in Port Glasgow.

Even though the big drydock was not completely ready, the opening of the shipyard took place on the planned date.

[13] The big drydock also known as Prins Hendrik-dok II would have a lift capacity of 8,000 tons and be suitable for ships of up to 500 feet length.

On 22 July 1905 Sliedrecht made its trials, and about two months later the Holland-Gulf Maatschappij contracted for the Alwina.

With all possible speed a slipway of reinforced concrete was ordered from the Hollandsche Maatschappij tot het maken van Werken in Gewapend Beton from Den Haag.

[21] For the RDM it meant that at that moment it was building the biggest ship to date constructed in the Netherlands.

[23] The construction, more specifically the riveting of the tanks, gave so much trouble that RDM and Firma Ph.

On 14 January 1925, a shipbuilding facility was set up as a subsidiary on the northern bank in Schiedam and continued to function as a separate establishment until 1978.

Two of the subs fell into German hands in May 1940, and duly served in the Kriegsmarine, the navy of Nazi Germany.

This apparatus allows subs to use their diesel engines under water, greatly extending their range, and subsequently all German U-boats were equipped with this.

The hall is now part of the so-called RDM Campus, a combination of research and development companies and a college.

During World War II, the company fell into German hands undamaged and intact, regardless of having been a major arms supplier to the Royal Dutch Navy.

The management decided to continue business as usual, although the representative of Queen Wilhelmina (who herself had fled to the United Kingdom), General Henri Winkelman, expressly forbade any work on German military projects.

A secret policy of clandestine opposition and dragging of feet was developed in the first months of the war, with the full support of the management.

In 1942 nevertheless, some 250 men had to go and do forced labour ('Arbeitseinsatz') in Germany, for shipbuilders Blohm und Voss in Hamburg.

As a result, the RDM was nearly completely wrecked: the floating docks were ravaged and sunk and all major cranes blown up.

The still viable components, the naval and the tool and heavy machinery businesses, were categorised in a new company: RDM Nederland BV, property of the government.

Naval construction got a large boost by the orders for four Walrus-class submarines for the Royal Netherlands Navy.

However, the proposed sale of four additional submarines to Taiwan worth US$6 billion failed to materialize, after the Dutch government blocked the purchase due to Chinese pressure.

On 20 December 1991, the company was sold by the government to the Royal Begemann Group of Joep van den Nieuwenhuyzen, and renamed RDM Technology Holding BV.

[26] The primary business of RDM had always been ship repair in its drydock facility, although it also built several new vessels over the years.