The military strategy of the Netherlands primarily focused on operations on land, and the role of the Royal Netherlands Navy was limited to defence of coastal waters. The naval strategy was centered around defence of essential ports, estuaries and coastal areas. Defensive minefields played an important part in this defensive strategy. For this, the Royal Netherlands Navy built a number of classes, starting with the Hydra -class. These minelayers were the first purpose-built minelayers, their predecessors were converted ships.

They gave good service during the neutrality period (1939-1940) in their role as minelayer, and especially Hydra was very active during the invasion of the Netherlands (May, 1940). However, this only covered up that these ships were old and did not have much fighting value left, and their subsequent careers were testimony to that. Only Medusa escaped to the United Kingdom where she was not given an active role, at a time when anything that could float and fight was pressed into service. Hydra was damaged and captured by German forces, but the Kriegsmarine did not bother to repair the ship, which was soon scrapped.

Hydra at sea, date and place unknown.

Construction details [1]

December 12, 1910

January 25, 1912

December 20, 1911

HW-1 (from October, 1946)
A-890 (from October, 1950)

[1]: Information taken from [VML] unless noted otherwise. Confirmed by other sources unless noted otherwise.
[2]: Pennants Medusa from [VAM]. Medusa was apparently not given a pennant during World War II.

Rammed and sunk by torpedoboat Z-3 in February, 1921. Salvaged April, 1921, returned to service 1923.
Involved in laying defensive minefields in Dutch coastal waters September 1939 - May, 1940.
Claimed one German aircraft shot down in Veerse Gat, May 11, 1940. [2].
Covered French torpedoboat L'Incomprise with anti-aircraft fire when former bombarded enemy shore positions near Waarde May 15, 1940. [2].
Bombarded enemy shore positions on Sint Philipsland May 15, 1940. [2].
Damaged by shore batteries from Sint Philipsland on May 15, 1940. Run aground to prevent sinking. Three crewmen killed in action. [2].
Refloated and scrapped Hendrik-Ido-Ambacht.

Involved in laying defensive minefields in Dutch coastal waters September 1939 - May, 1940.
Evacuated from Den Helder on May 14, 1940 with minelayers Jan van Brakel. Douwe Aukes. Nautilus and gunboat Johan Maurits van Nassau. Johan Maurits van Nassau was sunk by air attacks from German bombers.
Arrived Portsmouth May 19, 1940
Arrived Falmouth May 26, 1940. Laid up with only crews for anti-aircraft guns with Douwe Aukes and Van Meerlant .
Towed by tug Empire Henchman from Falmouth to Holyhead July 31 - August 2, 1940.
Training, depot and accommodation ship at Holyhead August, 1940 - February, 1944.
Transit from Holyhead to Shadwell Basin, London February 9 - 17, 1944.
Returned to Netherlands January, 1946.
Accommodation ship submarine service 1946 - 1950. [3]
Repair ship for minesweepers 1951. [3]
Stricken June 5, 1964. [3]
Sold for scrap September 25, 1964 to Jos Desmedt in Antwerp (Belgium). [3]

[1]: From [GB110] unless noted otherwise.
[2]: From [BOS1].
[3]: From [VML].