At the beginning of the seventeenth century, Portuguese ships rarely carried cannon. Their vessels were piled high with goods meant to make money, and when the two sides faced off, they still clung to the Middle Ages practice of hand-to-hand combat. The Dutch, meanwhile, avoided close combat whenever possible, preferring to bombard the enemy with cannon from a suitable distance. Their upper decks held no cargo, and the guns were operated by trained specialists.
It was hard to say which style of fighting was more effective. Newton had not yet been born, and there was no way to calculate trajectories. Gunners operated their cannon almost entirely through experience and luck. The Portuguese, meanwhile, lacked sufficient weapons and equipment. Even when they had weapons, they neglected them, letting them rust without maintenance.
These two methods of warfare influenced two other countries: Britain and Spain. Britain's naval tactics were closer to those of the Dutch, while the Spanish resembled the Portuguese. They built their ships like fortresses at sea, giving them an advantage in boarding actions.
Rivers were unlike the open sea. There was no room to widen the distance or deploy formations, and a ship's draft would also be affected. At times like this, the advantages of Spanish ships became apparent. Besides the vessels themselves, there were also land defenses such as blockhouses and gun batteries.
Though both were water, saltwater corroded iron far more severely than freshwater. Even iron forged into steel was still vulnerable to corrosion, so it had to be coated with rustproof paint or covered in copper like the bow of the Alert. Freshwater was relatively easier to deal with. Stainless steel was indeed corrosion-resistant, but it was expensive to forge; without cheap steel, it could not be used for construction.
During the Middle Ages, iron and