It chanced that a large number of vessels under Lumbres and Treslong were driven by stress of weather into the estuary of the Maas; and finding that the Spanish garrison of Brill had left the town upon a punitive expedition, the rovers landed and effected an entry by burning one of the gates.

The place was seized and pillaged, and the marauders were on the point of returning with their spoil to their ships, when at the suggestion of Treslong it was determined to place a garrison in the town and hold it as a harbour of refuge in the name of the Prince of Orange, as Stadholder of Holland.

On April 1, 1572, the prince's flag was hoisted over Brill, and the foundation stone was laid of the future Dutch republic.
William himself at first did not realise the importance of this capture, and did not take any steps to express his active approval; but it was otherwise with his brother Lewis, who was at the time using his utmost endeavours to secure if not the actual help, at least the connivance, of Charles IX to his conducting an expedition from France into the Netherlands.

Lewis saw at once the great advantage to the cause of the possession of a port like Brill, and he urged the Beggars to try and gain possession of Flushing also, before Alva's orders for the strengthening of the garrison and the defences had been carried out.
Flushing by its position commanded the approach by water to Antwerp.
When the ships of Lumbres and Treslong appeared before the town, the inhabitants rose in revolt, over-powered the garrison, and opened the gates.

This striking success, following upon the taking of Brill, aroused great enthusiasm.