Many countries had built screw-propelled steam ships that out-sailed and out-gunned everything the Dutch navy had.

The reaction by Smit van den Broecke was so quick that it probably reflected plans made earlier.

In May 1855 Smit van den Broecke presented an overall plan for the fleet at home and in the East Indies.

The heaviest ships of the new fleet would be 3 screw steam frigates of 400 hp, 50 guns and 500 men, to be stationed in the Netherlands.

The standard fighting warship for the East Indies would be a screw corvette of 250 hp, 12 30-pounders and 125 men, of which 12 would be built.

In 1859 Tideman claimed that the stiffness of the hull of the lead ship Groningen was 'only just satisfactory'.

Citadel van Antwerpen was built according to the rules for calculating dimensions, weights and shapes for a steam corvette described by Tideman in his 1859 work.

The Dutch National Archive has a lot of technical drawings of Vice Admiraal Koopman.

[6] In 1862 rifled muzzle loaders (RML) were introduced in the Dutch Navy, and being relatively modern, the class was re-armed.

In June 1857 Dordrecht and Leeuwarden were renamed on account of the 25 year remembrance of the Siege of Antwerp (1832).

[15] On 21 November 1864 Citadel van Antwerpen was brought into the Vlissingen Navy Drydock for inspection.

On 19 February 1865 workmen started to tow Citadel onto the patent slip of Vlissingen Naval Base.

[23] Citadel van Antwerpen arrived in Flushing on 14 August 1870, meaning she was finally back in service in 1870.

[24] On 23 March 1865 Vice Admiraal Koopman arrived back in Flushing from the Dutch East Indies.