From Wikipedia

Empire of the Seas
Episode Two

The Golden Ocean

During the early 17th century England's relative naval power deteriorated and a new threat emerged from the slaving raids of the Barbary corsairs, which the Navy had little success in countering. Charles I undertook a major programme of warship building, creating a small force of powerful ships, but his methods of fund-raising to finance the fleet contributed to the outbreak of the English Civil War. In the wake of this conflict and the abolition of the monarchy, the new Commonwealth of England, isolated and threatened from all sides, dramatically expanded the Navy, which became the most powerful in the world.