The Prince of Orange, however, was determined to relieve the city. Therefore, he sent a carrier pigeon into the city pleading for it to hold out for three months. To fulfil this promise, he planned to breach the dykes to allow the sea to flood the low-lying land. The siege could then be lifted using the rebel fleet, and the Spaniards would be forced to retire before the incoming sea. This tactic had also been used to relieve Alkmaar. The damage to the surrounding countryside would be enormous, and therefore the population of the area resisted the breaching of the dykes. However, in the end, the Prince prevailed and the outer dykes were broken on August 3. Previously, the Prince's Admiral Louis Boisot had assembled a fleet of more than two hundred small flat-bottomed vessels, manned by 2,500 veteran Dutch seamen, and carrying a large store of provisions for the starving townspeople of Leiden. Soon after the first dykes were broken, the Prince of Orange came down with a violent fever which brought operations to a halt. More importantly, the flooding of the countryside took longer than expected because of unfavorable winds. On August 21, the inhabitants of Leiden sent a message to the Prince saying that they had held out for three months, two with food and one without food. The Prince answered them, again by carrier pigeon, that the dykes had all been pierced and relief would come soon.