The Rules of Naval Warfare - Peloponnesian War
There were eight important rules under which the naval war would be conducted.
First, there were two vital theaters of war: Ionia, meaning both the mainland coast and the islands, and the Hellespont. Ionia was important because so many Athenian subjects were in this region. The Hellespont, a narrow body of water connecting the Black Sea and the Aegean, was the lifeline of Athens; through it flowed supplies and especially food from the shores of the Black Sea that the city needed to survive.
Second, money was vital to a naval war effort. For the Spartans, that meant securing Persian help even if it meant bargaining away Greek cities to Persian control. Persian cash meant pay for Spartan rowers, supplies, and even clothing. The amount contributed was huge: during one period, the Persians contributed 30 talents to keep 55 Spartan triremes in service for one month. Without this money, there would be no Spartan fleet and, consequently, no challenge to the Athenians. For the Athenians, it was vital to control their subjects who provided them with tribute. Their empire ensured that tribute would continue to flow into Athens to finance the Athenian navy, which protected the imports that literally kept the Athenians alive. For the Athenians, continued control of their empire was vital because it provided the necessary funds to finance their navy and offset Persia’s economic aid to Sparta. To supplement their revenues, both Sparta and Athens used their navies to collect extra money from both friendly and hostile poleis. In 411, Athenian forces were operating in Thrace, Thasos, and Macedonia, all in an effort to acquire money, through plunder if necessary. Not surprisingly, the more money plundered or collected, the happier the men and the better their morale.
Third, keeping a fleet well supplied was a very difficult job. Even a modest naval force of 30 triremes would have at least 6,000 men to feed. Money was vital because it paid for the necessary supplies. If tribute collection from states did not suffice, plundering enemy states of money or goods would substitute.
Fourth, it was vital for both sides to protect their allies and subjects from hostile attack so that these sources of goods and tribute would not be lost. This meant helping allied or subject states by providing soldiers or ships when necessary. It was also important to try to detach allies and subjects from their enemy. Various methods were used to seduce poleis. For example, Athens or Sparta could encourage either democratic or oligarchic revolutions through bribery, through a blockade, or by using military force or the threat of force to influence the local people within a given polis to overthrow a hostile government from the inside. Sometimes relatively small forces could bring about the necessary changes; in smaller poleis even three or four triremes with marines might be sufficient. Whatever the methods necessary, it was imperative to win over as many poleis as possible because new allies or subjects could then provide so many things vital to the war effort: supplies of all kinds, especially food, and tribute. At the same time, these things would then be denied to the enemy.
Fifth, possessing and maintaining naval bases was vital to all the operations just listed. A base had to have a good harbor, natural or manmade, to protect ships from storms and from the enemy. The harbor had to be easy to defend from land, and, if necessary, fortifications could be built on the spot. The base must also be close to the enemy or to hostile cities or astride vital sea lanes to permit soldiers to easily spot enemy movements and to launch attacks when the opportunity arose. Bases would provide the necessary space for crews to eat their meals and to sleep, both of which were impossible on board the narrow deck and in the limited space of a trireme. A base would also provide a place to repair damaged ships or merely a place to drag them on to land to dry them out, which was necessary from time to time. Bases could be used as supply depots and also as places to store equipment such as the sails when speed was of the essence. On one occasion, when the Athenians wished to attack Chios, they surrounded the island with a string of four forts: two were placed on the mainland across from Chios, another was built on a small island just off the island, and the last was on the island of Lesbos, to the north. These bases could be used to launch plundering raids on Chios and to intercept any shipping going to or from the island.
Sixth, the gathering of reliable information concerning the enemy’s whereabouts and movements was crucial. Bases could provide a place from which to keep a close eye on the enemy. Small lookout posts could be established in places of vital interest where there was insufficient space to establish a large permanent base. Since fleets usually hugged the coasts, lookouts could be established along the coasts watching well-traveled sea lanes. Because the Hellespont was so vital to their interests, the Athenians stationed lookouts on Lesbos and on the mainland coast across from the island to ensure that no Peloponnesian warships could pass north through the narrow channel towards the Hellespont. They also had lookouts at the entrance to the Hellespont. If an enemy fleet was sighted, they used fires to signal their admirals and the fleet, which were further into the channel, at a permanent base at Sestos. The Athenians also had nine triremes always on patrol in the Hellespont to watch for enemy vessels and to protect their merchant ships. Patrols were often sent out to spy on an enemy or search for an enemy. Information could be gleaned from other sources: neutral merchant vessels or local populations, whether friendly or unfriendly, could be mined for information even if bribery or force was necessary.
Seventh, new naval tactics developed over the course of the fifth century. There was the periplous (“sailing around”), in which fast triremes manned by experienced crews attempted to quickly outflank enemy naval lines and then swiftly change direction in order to ram enemy ships broadside. The diekplous (“sailing through”) was a similar tactic in which fast ships sailed into an enemy line between enemy ships and then suddenly turned to hit one of the ships broadside. The modern trireme Olympias has proven that such maneuvers were indeed possible. Generally, navies with faster ships and better crews preferred to fight in the open sea, where their speed and experience would be an advantage. Through most of the war, the Athenians had these advantages and often attempted to draw the Spartans ships away from coastal refuges. Often, navies would send out small groups of ships first to entice an enemy to sail out away from the coast and then surprise the enemy by having a larger number of ships suddenly appear on the scene. Sometimes entire fleets would sail out in an effort to provoke combat, heckling their opponents in the process; sometimes this type of direct challenge was so humiliating that admirals would feel obligated to fight. Marines also became an integral part of naval war. Hoplites would be stationed with the fleet, as would lightly armed troops and, sometimes, even rowers armed specifically for the occasion. Marines would be stationed on deck to prevent enemy soldiers from getting on board, and they would also seize opportunities to board enemy ships and take possession of them. It was considered a great coup if enemy ships could be captured intact, since they could obviously then be used in future battles. Squadrons in trouble could attempt to outrun enemy vessels, or they could quickly head for shore and beach their ships. They would then rely on their marines to hold off the marines of the enemy and to preserve control of the ships. If things looked dire, sailors often resorted to burning their own ships rather than allow them to fall into enemy hands. Blockades could also be used to trap the enemy ships in a narrow confined space, since without supplies the marines would either have to fight their way out or surrender.
Eighth, naval defeats could never weaken the power of the Spartan army and therefore could not threaten Sparta’s survival or its prosecution of the war. Persian wealth was practically inexhaustible, so the destruction of one fleet simply led to an influx of Persian money to finance a new one. For Athens, though, every naval battle threatened its very existence. After the Sicilian disaster, Athens no longer had the naval or economic resources to absorb more than one major defeat. One Spartan victory and Athens would lose its fleet, control of its empire, and the wealth the empire produced. Without its fleet, and without money to build new ships, the Athenians could not control vital trade routes and the supply lines upon which the city depended. In short, an Athenian defeat on the sea now meant an end to the war.