Mollema, in the "Honor Roll" calls him Joris Catz (without the "van"). He lived from about 1590 to 1654. He served the Admiralty of Amsterdam. He was a captain in 1621, Commandeur in 1640, and Schout-bij-Nacht in 1647.
In 1622, Joris van Cats was a squadron commander in the expedition of Pijnacker to Morocco. In 1630-31, he made two voyages as squadron commander to Muscovy. In 1631, he distinguished himself with Captain Vink against the Dunkirkers. In 1636-38, he commanded the Zutphen in the blockade of Dunkirk. In 1639, he distinguished himself as a squadron commander at the Battle of the Downs. In 1641-43, he was the blockade commander before Dunkirk. In 1651-52, he was fleet commander in the Mediterranean Sea, blockading the English in Livorno. He was replaced by Johan van Galen.
R.C. Anderson can give us some more insight into the latter event, in his 1963 Mariner's Mirror article, "The First Dutch War in the Mediterranean". This relies upon what Anderson has to say about Cats.
In August 1651, the Dutch decided to send a fleet of 15 ships, under Maarten Tromp's command, to the Mediterranean to defend Dutch sea commerce against the French. That did not actually happen. Instead, about October 1651, Joris van Cats was sent with 5 ships towards Cadiz. Tromp got sick, so he never arrived. There is a document, from the Rotterdam Admiralty, that mentions this deployment. They were actually going to send Tromp, in the Brederode (54 guns), along with other ships. Instead, the Dutch found that the English had hostile intent towards them, and so Tromp stayed in home waters.
Joris van Cats did not receive his orders to move into the Mediterranean Sea until 20 March 1652 (probably Old Style). Apparently on 27 June (I believe that this is the correct month) blockaded the English commodore Appleton in Livorno, with his squadron.
Appleton made the mistake to let Owen Cox, in the Constant Warwick take a French ship, outside the port. That offended the Duke of Tuscany, who demanded the ship's release. After the Constant Warwick left Livorno to careen at Genoa, Appleton was left with only two ships.
The Dutch, at home, were disappointed at Joris van Cats' lack of action. Johan van Galen was sent out, over land, to replace him. He arrived at Livorno on 22 August (Old Style), and led the fleet into battle, after only five more days.
From my unpublished document, Dutch Ships 1620-1700, we know something more about Joris van Cats' ships (this is only for what I have documentation):
1627-1629 Zeeland (30 guns plus 9 steenstukken), the crew varied from 90 to 105 men. The ship measured 200 lasts. The guns consisted of 6-18pdr, 6-12pdr, 12-8pdr, 4-5pdr, 2-3pdr bases, and 9 steenstukken (Jan Glete says that these were swivels, despite the name).
1636-1637 Zutphen (8 brass and 18 iron guns), crew of 110 salors and 20 soldiers.
1639 Zutphen (28 guns), the crew being 110 men.
1652 Jaarsveld (44 guns), the crew being 150 men.
- Dr. M.G. De Boer, De Kapiteinsjaren van Maerten Harpertszoon Tromp, Amsterdam, 1938.
- Dr. M.G. De Boer, Tromp en de Armada van 1639, Amsterdam, 1941.