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19th Century image of the mutilated Bloys van Treslong. On his chest the "Orde van de Unie"

Johan Arnold Bloys van Treslong (Steenbergen, November 8, 1757 – Amsterdam, 26 January 1824) was a Dutch naval officer and Patriot. He started his naval career in 1772 as midshipman with the Admiralty of the Maze. He served the Dutch Republic on the North Sea, in the West Indies and in the battle with islamic pirates in the Mediterranean.

In 1781 he fought in the naval battle of Cape St Mary under the command of Pieter Melvill van Carnbee and from 1782 till 1787 he was commander on several ships in the Mediterranean. Because of his support for the Patriots he was laid off in 1787. This unfavour lasted until 1793. After the defeat at the Battle of Camperdown in 1797 he was made scapegoat but later on his reputation was restored.

The Battle of Camperdown (Kamperduin)

Sailing ship of the line Brutus, Treslong escorted the squadron of commander-in-chief of the Batavian fleet, Vice admiral Jan Willem de Winter (1761–1812), as Schout-bij-nacht of the "White flag", the 7 October 1797. The committees of Navy and Foreign affairs had ordered the fleet to break the British blockade of the Dutch coast. At Camperdown they met a much stronger British fleet under admiral Adam Duncan.

Duncan acted in a manner that was imitated later by Nelson at Trafalgar; he thinned out the poorly coordinated and badly sailing Batavian fleet. The British ships set course perpendicularly towards the Batavian ships and shot them to pieces. The flagship De Vrijheid (Freedom) was included by four British ships and one after the other Batavian ship was devastated by the excellently navigating and firing enemy.

Bloys van Treslong could not reach the flagship, located against the wind, because he was impeded by a burning and rudderless Dutch ship, the Hercules with 74 cannons. A cannonball shattered the rear admiral’s right arm, which had to be amputated.

The British fleet gained a sounding victory; ten Batavian ships were captured, among which nine ships of the line and there were almost 1400 Dutch casualties. On English side not one ship was lost, but more than 1000 casualties were counted. For the first time in history a Dutch admiral had lost his flagship. Admiral de Winter and his crew were taken prisoner and were brought to Great Yarmouth. The rear-guard under Bloys van Treslong, reduced to three heavily damaged ships, managed to sail to Hellevoetsluis.

Consequences of the battle of Camperdown

The Batavian republic had been deeply shocked by the defeat. The government, the Staatsbewind, that was responsible for sending a fleet that was too weak, wasn’t to blame in the eyes of the parliament, the press nor the public opinion and admiral de Winter was considered a hero. Thus, all the blame fell on the head of rear admiral Bloys van Treslong. That he was an aristocrat did not improve his popularity in this revolutionary period. He was blamed for having navigated poorly and to have given the English the opportunity to cut through the Dutch line as a scythe. He was also accused of not having assisted the surrounded flagship and he had to appear before the naval high tribunal.

The court-martial cleared admiral de Winter of responsibility for what had happened. Other officers got a disciplinary sentence. In the eyes of the military judges Johan Arnold Bloys van Treslong was to blame for all that went wrong. In spite of a competent defence and convincing arguments he was declared guilty and sentenced for up to five years suspension and payment of a part of the process costs. It took more than ten years for Bloys van Treslong to be rehabilitated under the reign of king Louis Bonaparte.


Rehabilitation took place on 18 October 1808 in the form of an appointment as (titular) Vice Admiral. On that very day he was honourably dismissed and was pensioned at the age of 61. He was also dubbed knight in the "Order of the Union", the honour which he shared with his relatives Cornelis Ysaac, Jacob Arnout and Willem Otto.


Bloys of Treslong is a family that descended from a bastard son of John of Beaumont. The Bloys of Treslong included four flag officers in the Dutch marine.

  • Willem Bloys van Treslong (1529–1594), a captain of the Gueux de mer
  • Jacob Arnout Bloys van Treslong (1756–1826), also called Jacob Arnold Bastingius, was a Secretary-General of the Dutch Navy
  • Johan Arnold Bloys van Treslong (1757–1824). Schout-bij-nacht at the Battle of Kamperduin.
  • Jhr. William Otto Bloys van Treslong (1765–1837), an uncle of Johan Arnold.


  • Cornelius Ysaac Bloys van Treslong (1763–1826) made it to Captain in the Batavian and Dutch Navy.

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