The cardinal had taken the field with an army of fifteen thousand foot and three thousand horse, assembled at Valenciennes, and after hesitating some time whether, or not he should attempt to relieve La Fere, he decided instead on a diversion.  In the second week of April; De Rosne was detached at the head of four thousand men, and suddenly appeared before Calais.  The city had been long governed by De Gordan, but this wary and experienced commander had unfortunately been for two years dead.  Still more unfortunately, it had been in his power to bequeath, not only his fortune, which was very large, but the government of Calais, considered the most valuable command in France, to his nephew, De Vidosan.  He had, however, not bequeathed to him his administrative and military genius.

The fortress called the Risban, or Rysbank, which entirely governed the harbour, and the possession of which made Calais nearly impregnable, as inexhaustible supplies could thus be poured into it by sea, had fallen into comparative decay.  De Gordan had been occupied in strengthening the work, but since his death the nephew had entirely neglected the task.  On the land side, the bridge of Nivelet was the key to the place.  The faubourg was held by two Dutch companies, under Captains Le Gros and Dominique, who undertook to prevent the entrance of the archduke’s forces.  Vidosan, however; ordered these faithful auxiliaries into the citadel.

De Rosne, acting with great promptness; seized both the bridge of Nivelet and the fort of Rysbank by a sudden and well-concerted movement.  This having been accomplished, the city was in his power, and, after sustaining a brief cannonade, it surrendered.  Vidosan, with his garrison, however, retired into the citadel, and it was agreed between, himself and De Rosne that unless succour should be received from the French king before the expiration of six days; the citadel should also be-evacuated.

Meantime Henry, who was at Boulogne, much disgusted at this unexpected disaster, had sent couriers to the Netherlands, demanding assistance of the States-General and of the stadholder.  Maurice had speedily responded to the appeal.  Proceeding himself to Zeeland, he had shipped fifteen companies of picked troops from Middelburg, together with a flotilla laden with munitions and provisions enough to withstand a siege of several weeks.  When the arrangements were completed, he went himself on board of a ship of war to take command of the expedition in person.  On the 17th of April he arrived with his succours off the harbour of Calais, and found to his infinite disappointment that the Rysbank fort was in the hands of the enemy.  As not a vessel could pass the bar without almost touching that fortress, the entrance to Calais was now impossible.  Had the incompetent Vidosan heeded the advice of his brave Dutch officers; the place might still have been saved, for it had surrendered in a panic on the very day when the fleet of Maurice arrived off the port.