Why were cannons useful

Cannons are weapons that were able to be used defensively and offensively for many decades. When being used to attack, they could put on all sides of ships, allowing ships to deal intense ranged damage, while also could be pushed onto a battlefield. In defense, they could be placed in strategic positions on coasts, fortresses, or fields.

Cannonballs, the projectile fired from cannons, were typically either made of solid iron or had gunpowder encased in iron.