William of Orange then briefly indicated his plan; adding that he had no fears for the result; and assuring his friends, who expressed much anxiety on the subject, that if Parma really did attempt the siege of Antwerp it should be his ruin. The plan was perfectly simple. The city stood upon a river. It was practicable, although extremely hazardous, for the enemy to bridge that river, and by so doing ultimately to reduce the place. But the ocean could not be bridged; and it was quite possible to convert Antwerp, for a season, into an ocean-port. Standing alone upon an island, with the sea flowing around it, and with full and free marine communication with Zeeland and Holland, it might safely bid defiance to the land-forces, even of so great a commander as Parma. To the furtherance of this great measure of defence, it was necessary to destroy certain bulwarks, the chief of (10th June, 1584) which was called the Blaw-garen Dyke; and Sainte Aldegonde was therefore requested to return to the city, in order to cause this task to be executed without delay.
Nothing could be more judicious than this advice. The low lands along the Scheldt were protected against marine encroachments, and the river itself was confined to its bed, by a magnificent system of dykes, which extended along its edge towards the ocean, in parallel lines. Other barriers of a similar nature ran in oblique directions, through the wide open pasture lands, which they maintained in green fertility, against the ever-threatening sea. The Blaw-garen, to which the prince mainly alluded, was connected with the great dyke upon the right bank of the Scheldt. Between this and the city, another bulwark called the Kowenstyn Dyke, crossed the country at right angles to the river, and joined the other two at a point, not very far from Lillo, where the States had a strong fortress.
The country in this neighbourhood was low, spongy, full of creeks, small meres, and the old bed of the Scheldt. Orange, therefore, made it very clear, that by piercing the great dyke just described, such a vast body of water would be made to pour over the land as to submerge the Kowenstyn also, the only other obstacle in the passage of fleets from Zeeland to Antwerp. The city would then be connected with the sea and its islands, by so vast an expanse of navigable water, that any attempt on Parma’s part to cut off supplies and succour would be hopeless. Antwerp would laugh the idea of famine to scorn; and although this immunity would be purchased by the sacrifice of a large amount of agricultural territory the price so paid was but a slender one, when the existence of the capital, and with it perhaps of the whole confederacy was at stake.