Sea-raiders have roamed the high seas for centuries. Back then, private seafaring individuals in armed ships waged war at sea, usually against the enemy’s maritime trade. Around the world, raiding the ships of a sovereign or ruler’s enemy during war time was an accepted and common practice.

What is a pirate?

Sea-raiders who raided ships without the authorisation of a sovereign or ruler were historically considered pirates. The Latin phrase hostes humani generis, (translated in English as ‘enemies of all mankind’) reflected the historic understanding of a pirate as a sea-raider with no allegiance to any sovereign or ruler.

Until the early 18th century, western laws considered pirates traitors rather than criminals. Since sea-raiding was a legitimate practice during war time, raiding without a ruler's authorisation was an act of treason, not the crime against property it is today.

For centuries, the use of authorised sea-raiding across the world and the fluctuating nature of conflict meant the distinction between an authorised sea-raider and a pirate was not always clear. Pirates tended to gain the ruler's attention during peace time, when the end of a war caused legitimate employment opportunities to dry up and their continued raiding affected peace agreements and treaties.

In 1717, to combat a rising tide of piracy in the Caribbean colonies, the British changed their piracy law to remove treason and focus piracy as a crime against property: robbery at sea. This shift towards a property crime formed the foundation of the international law of piracy used today.

Today, a pirate is still an individual raiding ships at sea without authority. It is the source of that authority that has changed. Instead of sovereigns and rulers, states are now responsible for controlling the actions of their inhabitants at sea. In addition, a much broader variety of criminal acts are now legally included under the piracy label, including:  threatening or using violence, breaking and entering, robbery, seeking ransom, kidnapping, hostage taking, grievous bodily harm, assault, and murder.


A person is now a pirate when committing piracy on the high seas: the vast expanses of ocean that lie outside the jurisdiction of any state.

Notorious pirates of the 18th century

These etchings were first published in the Dutch version of Captain Charles Johnson's A General History of the Robberies and Murders of the Most Notorious Pirates in 1725. Johnson's book forms the basis of knowledge about Caribbean pirates at this time. However, its legitimacy and accuracy (including these images) can not be verified. Neither can Captain Johnson's identity.


Why did sea-raiders become pirates?

Some sea-raiders turned to piracy as an act of protest against the dire conditions of legitimate employment. Others became pirates as a solution to the unemployment caused by peace. However, most seafarers simply became pirates when their ship was captured by other pirates.

Piracy appealed to seafarers because it offered them an unprecedented level of autonomy over their own lives combined with the potential for financial reward.


Working on ships at sea was a hard and unrewarding life. Many seafarers worked for months without payment and endured harsh discipline and violence at the hands of captains and superiors. In contrast, pirates tended to democratically elect their captains, make group decisions on where to raid, and receive agreed upon shares of prizes. When these motivators combined with the absence of authority and control from the sovereign or ruler, the appeal of piracy heightened with the lowered risk of being caught.

From the mid-19th century, the decline and eventual abolition of authorised sea-raiding in Europe solidified the perception of pirates as criminals. However, in some regions where locals still engaged in authorised sea-raiding (such as the Persian Gulf and the East Indies), colonial powers branded these local sea-raiders pirates to facilitate the expansion of their colonial and economic interests.


Today, pirates are widely considered criminals. The prevalence of the international law of piracy overrides any justification the pirates may make for the legitimacy of their actions. The problem today is typified by the absence or weakness of state authority to control citizens at sea. See Somali pirates for more information.

What could be done about pirates?

Pirates created a dilemma for rulers and sovereigns. On one hand, their exceptional seafaring abilities and great daring made their skills highly useful for taking the prizes that funded the numerous wars that broke out. On the other hand, pirates’ illegal sea-raiding during peacetime undermined fragile peace treaties and created diplomatic headaches.

Their skills made them very difficult to stopInstead of capturing and prosecuting pirates, rulers often offered them amnesty. Many pirate captains and their crews switched between authorised sea-raiding and piracy according to their personal circumstances and the geo-political environment of the time.

How to be a successful pirate

During rare periods of extended peace, sea-raiders had a choice: continue their allegiance to a ruler and obey the law, or continue their sea-raiding without authorisation by becoming pirates. In making this choice, sea-raiders needed to consider the following, intermingled factors:


Rule 1: Suitable geographic conditions

Successfully taking prizes required two essential factors: predictability and the element of surprise. Predictability came from the established maritime trade routes that all seafarers used during certain times of year based on the prevailing winds and favourable currents. To utilise surprise, sea-raiders utilised chokepoints: areas on trade routes that forced ships through narrow channels between islands or mainlands, such as in the islands of the Caribbean, the Malacca Strait and the Gulf of Aden. Chokepoints isolated and separated ships from each other, allowing a skilled sea-raider to surprise, overtake and overcome a target ship. 

You can see how piracy coincided with favourable currents on the maps below. The diamond symbols represent chokepoints used by pirates and the brown clouds their land bases. Scroll over for details and double click for a larger view.

Chokepoints and trade routes of historical piracy hotspots

Irish piracy, c.1600
Irish piracy, c.1600

The remote regions of southern Ireland fell outside of English authority. Pirates took advantage of the steady stream of shipping traffic returning from the New World and utilising the Gulf Stream.

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Caribbean piracy, 1700s
Caribbean piracy, 1700s

The Caribbean had a wealth of chokepoints that forced ships travelling to New Spain through the channels separating the outer islands.

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Malacca Strait, 1990s
Malacca Strait, 1990s

Indonesian bandits and pirates from the Riau islands took advantage of the Malacca Strait's numerous islands to lie in wait for ships.

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Irish piracy, c.1600
Irish piracy, c.1600

The remote regions of southern Ireland fell outside of English authority. Pirates took advantage of the steady stream of shipping traffic returning from the New World and utilising the Gulf Stream.

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Rule 2: Favourable political conditions


While all sea-raiders utilised these geographical conditions, to succeed as a pirate, they needed friends on land. Pirates used sympathetic land bases to hide, resupply, repair and clean their ships, sell their prizes, and rest and recover. There are many examples of land-based authorities being complicit in piracy. 


Rule 3: Ungoverned spaces

Rule 1 and 2 needed to coincide with areas of fluctuating, minimal, lax, or non-existent authority. These usually occurred on the fringes of a ruler's territory, in distant colonies where the strength of the ruler's direct authority was diluted, or in areas outside of any rulers' authority at all (map).

Rule 4: A high risk/reward ratio

Sea-raiders usually operated on a 'no prize no pay' policy, so the value of their prize needed to be worth more than the risk involved in capturing it. For pirates, rules 1 - 3 combined to lower the risk of capture yet retain the value of the prize. Unlike authorised sea-raiders, pirates only shared the prize among themselves. So a prize of a Spanish gold bullion ship could be all that the pirates' needed to retire from the business. 


Piracy epidemics from the 17th century Caribbean to 21st century Somalia occurred because all these factors combined to make the choice of piracy an easy one to make. 





Next page: Authorised sea-raiders