In 1625, in the Battle of San Juan, the Dutch commander Boudewijn Hendricksz tested the defenses' limits like no one else before. Learning from Francis Drake's previous failures here, he circumvented the cannons of the castle of San Felipe del Morro and quickly brought his 17 ships into the San Juan Bay. He then occupied the port and attacked the city while the population hurried for shelter behind the Morro's moat and high battlements. Historians consider this event the worst attack on San Juan. Though the Dutch set the village on fire, they failed to conquer the Morro, and its batteries pounded their troops and ships until Hendricksz deemed the cause lost. Hendricksz's expedition eventually helped propel a fortification frenzy. Constructions of defenses for the San Cristóbal Hill were soon ordered so as to prevent the landing of invaders out of reach of the Morro's artillery. Urban planning responded to the needs of keeping the colony in Spanish hands.