On 10 July 1639, Captain Forant was with Tromp's main body of ships:
- Adm. Tromp
- Witte de With
- Jan Evertsen
- Rear-Adm Willem van Coulster
- Captain van Dieman
- Jan Theuniszoon Sluis
- Matijs Gillissen
- Theunis Post
- Keert de Koe
- Lambert Ybrantszoon Halfhoorn
- Captain de Zeeuw
- Jan Pouwelszoon
- Sijbrant Barentssen
- Jan Garbrants
- Captain Backhuijsen
- Captain 't Hoen
- Pieter Pieterszoon
- Jacques Forant
- Tjaert de Groot
On 1 October 1639, Captain Forant reported to Tromp that English nobles on shore said that 6 or 7 Dunkirk frigates had arrived to take soldiers from the armada to Dunkirk.
On 2 October, Captain Forant received 20 soldiers from a group of 160 that had arrived, having been part of the garrison of den Bos.
On 3 October, Captain Forant was assigned to a squadron commanded by Joris van Cats: Cornelis Engelen Silvergieter, Sijbrant Waterdrincker, Dirck Claeszoon van Dongen, Frans Janszoon, Jacques Forant, Captain Regermorter, Commandeur Johannes Hend., Captain de Nijs, Lieuwe de Zeeuw, Captain Juynbol, and Captain Melcknap, and others. On 12 October, Rear-Admiral Cats lead the attack on the Flemish admiral: Joris van Cats, Jacques Forant (Overijssel, 26 guns), Jacob Turcquois, a fireship, Jan de Lapper, Captain Schllinghout, Elias Balck, Captain Melcknap, and Pieter Janszoon van den Brouck.