In the Caribbean, the use of privateers was particularly popular. The cost of maintaining a fleet to defend the colonies was beyond the capabilities of national governments in the 16th and 17th centuries.
These governments therefore granted private vessels a letter of marque (or commission of war) authorizing them to capture enemy ships. They kept most of the spoils, with the rest going to the sponsoring government. These ships operated independently or in fleets and if successful, the reward could be substantial. When Francis Drake captured the Spanish convoy of silver at Nombre de Dios (port of Panama on the east coast) in 1573, his crew became rich for life.
The possibility of such gains attracted wealthy businessmen and nobles who were all willing to fund this legal piracy in exchange for a share of the profits. The sale of the captured goods was also a good economic contribution for the colonies.
Race War
Privateering has often been used by a belligerent to make up for the insufficiency of its resources against an adversary with naval supremacy.
This was the strategy of the French against the English for much of the 18th century and during the wars of the Revolution and the Empire.
Similarly, during the two world wars, the German navy fitted out merchant ships for the war on Allied commerce in secondary theaters where the traffic was not organized in convoys (Indian Ocean, Pacific, South Atlantic). The adventures of these corsairs will generally be picturesque but without much consequence on the course of the two conflicts
Corsair ships
Corsairs, wrongly confused with pirates, are in a way mercenary sailors. As such, they used generally small, fast, maneuverable, and stealthy ships to execute boarding at sea more by surprise than by force. When "fortune" smiled on them, they could take off boats of high tonnage (the emblematic capture of Kent by the flute La Confiance of Robert Surcouf on August 31, 1800) but often merchants, not conducive to their activity and which they resold often.