A number of geographic and economic characteristics of the classical world produced an environment that encouraged piracy. First of all, "The coasts of the Mediterranean are particularly favorable to the development of piracy." The barren, rocky shoreline was not suitable for large scale agriculture and could not support a large population. Therefore, most villages were small and of humble means. Being coastal villages, the primary method of support came from fishing, so most of the able-bodied men had boats, seafaring skills, and navigational knowledge. When fishing wasn’t enough, many men turned to highway robbery and raids of nearby territories to support themselves. However, land trade routes were few and far between, given mountainous obstacles and few rivers. Therefore, most nations deemed "the principal lines of communication should be by sea, and the bulk of commerce should be carried by the same routes."
In the early days of maritime navigation, most trade vessels hugged the coasts. "Traffic was restricted to fixed lanes in a way impossible on the open ocean." The naukleroi, or ship-owning merchantmen, moved slowly along established trade routes with their heavy burdens weighing them down. Imagine a fisherman-raider seeing treasure-laden trade ships passing the shores he knows like no one else, day after day. With the motivation and the means to do so, it wasn’t hard for coastal natives to apply themselves to sea-robbery. They brought a thief's mindset to the sea and simply changing their method of thievery. "The pirate was the robber of the sea highways: and the highways of the Mediterranean were well-defined and well-traveled."
The rocky coast that had been unsuitable for agriculture was perfectly suited to piracy, outfitted with hidden inlets that allowed quick access points to trade routes. "Pirate enclaves grew up along rocky shores that provided shelter and kept them hidden from view until it was too late for their victims to escape."
These early maritime raiders were at the same time the first true pirates, attacking anyone of any nationality, owing loyalty to no one, but also quite unique. Because of their roots in land raiding, they were known not only to attack ships and coastal towns but also to venture further inland. This caused even the earliest large cities to relocate anywhere from 2 to 10 miles away from shore. Pirates tended not to go any farther inland due to difficulties escaping. Speed was one of the most important elements of piracy. This relocation gave a relatively effective cushion of safety to major cities such as Athens, Tiryns, Mycenae and others. It protected them from the sea's dangers, although it also cut them off from its benefits. The sea was still the primary, and practically only, area of major commerce. This caused twin cities to be built, one inland city paired with a coastal port, such as Rome and Ostia, Athens and Piraeus, etc. To protect their connection they built "‘long walls’ like those that enclosed the thoroughfare between Athens and Piraeus." The maritime historian Henry Ormerod said, "If we remember that piracy was, for centuries, a normal feature of Mediterranean life, it will be realized how great has been the influence which it exercised on the life of the ancient world."
Despite these efforts, they couldn’t completely remove contact between the pirates and the ports. Since they couldn’t effectively disrupt the pirates "business," it only continued to grow. Men often joined the very pirate ships that attacked their own towns. Even the sailors on merchant ships attacked by pirates turned to piracy themselves when they were out of work. Piracy offered a free and lucrative career, a chance for those who were interested to try to change their lives and better their livelihood a hundredfold in a very short time. For example, the area around Crete, famous for its slave markets, was known as "the Golden Sea" because of how profitable the slave trade was Unsurprisingly, Crete was also notable for its pirates. In point of fact, if a city had a successful slave market it was most likely a pirate port. Notorious pirate havens like Cilicia and Delos had thriving slave markets. "According to Strabo, as many as ten thousand slaves were sold in Delos in just one day." Being kidnapped by pirates and sold into slavery was so common that it was a favorite theme of ancient Greek dramatists.
Piracy had become something of a bogeyman, and defence from pirates is frequently given as one of the reasons for cities to set up honorific decrees for individuals, as with the c. 166 BC decree from Imbros: ""Lysanias is benevolent towards the people […] he stood firm and brought news of the descent of pirates"
The phenomenon was particularly endemic in certain areas, notably Cilicia (southeastern Turkey) and Illyria (western Balkans) There is evidence that "the coastal Illyrian tribes had created their own type of vessel, the lembus, in which to carry out their depredations." It was a small, fast ship built to serve the purpose of quickly emerging from or retreating to hidden inlets to attack heavier vessels.
Illyrian piracy could be more correctly termed privateering, as it was endorsed by the state. In Polybius’ Histories, which covers the period of 220–146 BC, his description of Teuta, Queen of the Illyrians states "Her first measure was to grant letters of marque to privateers, authorizing them to plunder all whom they fell in with."
"So powerful did the Illyrians become that by 230 BC no honest traders wished to participate in maritime commerce." Rome's attention was on land based conquests, and they did not initially seek to become the naval police that Rhodes and previously Athens had been for the Greek islands. However, when Illyrian forces attacked a convoy of ships with grain intended for the military, the Senate decided to send two envoys to Queen Teuta, who promptly had one killed. Outraged, "Consul Gnaeus Fulvius sailed for Illyria with two hundred ships, while Consul Aulus Postumius and 20,000 soldiers marched overland." By 228 BC, Teuta had surrendered, and the Romans had decimated the forces of one of the most notorious pirate havens in the Mediterranean.